Opinions please

Rather than packing up and moving, checking out and checking in and then checking out again, losing precious daytime to the logistics, how about staying in Florence for four nights and doing Siena as a day trip? It's only about a one hour bus ride between cities. If you take the bus from Florence to Siena, it lets you off in a piazza near the top of town, in the middle of the older part of the city. If you take the train, you have to climb up stairs from outside the older part of the city, or take escalators or find a taxi. Bus is easier.

This is the type of question that is very difficult to answer since we know nothing about your interests. We have spent several days in Florence and would easily go back. Lots to see and do in the area from typical tourist sites to surrounding wineries. Siena a little less so but still a good day trip from Florence. For someone interested in doing a drive-by -- Yep !! Saw that !!! Two days is more than enough. Even one day probably is adequate. What you want to see and do tends to be personal. I could spend a week in Florence but two days might be too much in Siena.

Two nights anywhere is not too much, figure that gives you only one uninterrupted day, your arrival day is mostly lost due to getting settled and jet lag, and the day after your second night you are focused on moving to the next location.

You do not mention what it is that attracts you to spend 3 weeks in Italy, but Florence probably has plenty of it, if you look. Certainly there is plenty of wandering around to do, the Duomo is worth a look, even if you are not an art fanatic, going to the Accademia museum to see David is worth it.

Same with Siena, I could spend two nights there just having a glass of wine and wandering around.

But to your original point, are you going to a place like Siena just because others say it is a place to go? Or do you have some interests...churches, history, quaint Italian towns, food, ancient history, art, markets, wine?

Then establish an itinerary that exploits those interests. My other advice is do not be afraid to slow it down a bit, two night stays should be a minimum, 3 or 4 nights better, much of Italy is centered on "la Dolce Vita" savoring the sweetness by not doing much of anything...otherwise, after a week and a half, you will be exhausted and at each others throats.

If you are not that interested in art and museums, you'd better stay in Siena and make a day trip to Florence. In one day you can walk around the Signoria Square, cross the Bridge, spend 30 minutes in the Accademia Museum to log the David as "done", eat a famous sandwich and get on a train back to Siena in time for dinner.

In Siena You can easily rent a car and explore the Tuscan countryside for a day. Two-for-one: You could see the countryside and save some time by driving south from Siena, to drop the car close to Rome and jump on a local train.

2 nights each is good but, you'd be better off staying in one the whole time and visit the other. Packing-up, route finding and checking-in/out takes up a chunk of time that could be better used for enjoying your trip as the two locations are just an hour apart. If you enjoy a semi-urban setting, stay in Florence, if you enjoy the country-side type setting, stay in Sienna.

Checking out the art offerings doesn't mean you need to be a fanatic; the Rick Steves self-guided audio tour of the Ufizzi pretty much hits the highlights, giving you a speed-run without dwelling on the esoteric. We're not talking modern art here where you need to contort your head into different angles or, take a mushroom beforehand so that you can gain the proper perspective. This art is historical, what was done in the Renaissance was techniques/methods/perspectives that had been lost then rediscovered from Roman times. What was accepted then, was lost/banned/abolished during the Middle Ages, then rediscovered.

We aren’t huge art museum fanatics so we’re wondering if 2 days and nights are too much.

I think others have asked the important question. What exactly do you want to see? If it is just wandering around the cities, I would agree that a day trip to Siena is enough and stay in Florence and head to Rome from there.

Don't miss the statue of David, the Duomo and Baptistry in Florence. Be sure to visit the Central Market and have lunch there. I recommend Nerbone for a delicious sandwich. There is plenty to see in Florence versus Siena, although Siena is very much worth a day trip. Don't skip it.

Adding my 2 cents.

March weather may be a factor in your travels. Pack accordingly.

Lots to see and explore in both cities without seeing art museums. David is a must though. Get your reserved tickets prior to your departure. I found The Bardini Museum of interest. Research to see if you’d care to explore. By per chance while lost I discovered the impressive frescos in the tiny Buonomini de San Martino church.

See if the monks are still allowing people to view their gregorian chants at the Basilica San Miniato al Monte. Great view over Florence from the nearby Pizzalle Michelangelo.

Personally I found strolling around the adjacent Porte Sante cemetary fascinating. I also enjoyed wandering about that side of the Arno. Found a sweet bar/cafe where I had a wonderful shot of expresso. Teeny tables outside to sit and be immersed in the reality you are in Florence.

Lastly, seeing artisans at work was another highlight of my Florence stay. By nature I wander. Over the years such exploration has provided simple pleasures of discovery.

EDIT: meant to say throughly enjoyed my meals at the Taverna A De’ Neri and Trattoria II Bargello….both places found roaming ….the latter was especially rewarding in ambience, service and taste.

EDIT: Lucca is an easy day trip from Florence. After walking a portion on the wall that surrounds the city, hopped on a rented a bike to explore. My travel month was October. Was chilly but no rain. Worth considering if weather is conducive.

All the places you mentioned need more than two days each. You state you will have three weeks in Italy so I wonder where else you are staying and visiting!

Since you’re asking for opinions, we prefer Siena more than Florence. Also, I love the ambiance of a city at night, so I wouldn’t want to miss Siena by just taking a day trip.

You need at least two nights in Florence since that’s where you’re staying with jet lag. Another option would be land in Florence and immediately take the bus to Siena for your first two nights. (We have flown from Seattle and taken up to three trains to reach our first destination; it’s doable.). Then you are spending your initial days in Siena before heading to Florence and later to Rome.

If the rest of your locations during your trip are larger cities, I would definitely say to not miss staying in Siena.

The best advice I can give is to determine what YOU want to do in each of those locations. That will give you the answer where to stay and how long. Have a great time!

Two days in Florence too much, OF course NOT, Florence is amazing, lots to see. Just doing the city itself, the Bapistry, Doumo, San Croche and the
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Siena is great, loved climbing the tower. You might consider doing Siena on a day trip from Florence.

Personally, I would not go all the way to Italy and only spend two nights in Florence, especially when the first night is your arrival night.
That leaves you with one day only.
Even if you don't go to any museums, you can wander around Florence and see lots outdoors and in the markets, at the river, in the Oltrarno area, etc.
I've been to Siena twice, and found it underwhelming compared to Florence.
What are your interests in going to Italy?, given that the whole country is full of amazing art and museums and galleries?

We went to Italy for the first time in 2019. One of the very few things I regret is scheduling only two nights in Florence. My paradigm for travel now is to try to spent at least three night but preferably four in any one place.

A walk through the Boboli gardens in Florence is worth doing. Ditto the central market. So there’s almost a day.

The most fantastic fine arts museum on the planet (and I don’t believe I’m over stating this) is the Uffizi Gallery in Florence. The Uffizi is my first stop in Florence and the Accademia (David) is my second. I will never get bored with either place. It is a cultural experience like no other and I too am not a big museum person. Both the Uffizi and Accademia are exceptions.
I also prefer sleeping in Siena because it’s special after the day trippers leave. Asking for a lemoncello to go when leaving your restaurant after dinner to sip as you stroll through the piazza then sit on the pavement as the others is the perfect way to end the night.
Both Florence and Siena are not to be hurried. You can take a direct train from Florence to Rome (1h 45m) or a direct bus from Siena to Rome (3h). However, I don’t know if there will be enough room for your luggage if traveling by bus.

In direct opposition to the RS travel mode. Less is more!
Day one: get there, find the hotel , get into your room, unpack (?) and then go out. Half the day or more is gone.
Day two: Get up, breakfast, shower and get read for the day. pack, store you luggage. Wander around for a little bit and the find your luggage and move on to the nest stop. Not much time to explore a city.
My recommendation is to add, at a minimum, one day or two to the middle. you can then ENJOY the city you are in and have a relaxed stay, enjoy and long dinner (as the Italians like it) and explore the city.
Just one man's opinion who has travel a lot!
Enjoy your time!!!!!!!

Also, be careful that you don't spend all of your three weeks getting from A to B. Leave something to come back to...