We have traveled in Italy and Switzerland many times, each time staying for 1-2 months. Over the years we have set a few rules that help us enjoy our trips. It's a lot of time and work to move from one city to another, so we have a rule to never stay 1 night unless it's to catch a flight home. If the city is worth the visit, we always try to stay 3 nights or more. Otherwise, it's a day trip from one of our cities we're using as a base. You're going to 14 or 15 cities in 5 weeks. That's a lot of moving, each time eating up hours and hours of valuable sightseeing time. For a 5 week trip, we would limit the number of locations to 5-6, maybe stretch it to 7. Most people try to do too much and yes, they got there, but what did they experience, what did they leave out, and how fast did that trip go?
Having been to Rome about 10 times, there's always another layer to experience. So we can never go for less than a week. But, we realize you're trying to do a lot with 5 weeks. Read Rick's book regarding Ostia Antica or my review on Trip Advisor. It's great and is worth a whole day.
We've been to Sorrento and Pompeii by taking a day trip from Rome. That was plenty of time. I haven't been to Capri, so if you're adding that as a day trip, that's another day.
Orvieto is a 2 night quick visit. That gives you a day to get there, a day to explore, and a day to leave. (Try to make a reservation at Trattoria del Moro Aronne. Try the nidi! See Rick's book.)
You may have a strong reason to go to Assisi and if so, do go, but it's a long way east, and then a long way back. It takes you out of the way. I think it's worth 1-2 hours. That's all the tours give it.
We loved Siena and spent a week there, but it was a relaxing week where we were able to walk to every gate, visit every sight they had, especially the Duomo, and just sit at the Fortezza every night and soak up the pace of the people. We took a day trip to the hill town, Montalcino, for a wine tasting. Your 5 days is good if you have plans. (If you get there, find All'Orto de Pecci for a great meal with locals down in a valley.)
Florence has so much to see, but crowds that make it difficult. Five days is low if you are also doing day trips to Lucca and Bologna. We took a day trip to Bologna because I always wanted to go. I was disappointed. Lucca is a very different experience. I love it there. Someone mentioned Ravenna. I can't get enough of Ravenna. See my review on Trip Advisor for a good route if you decide to go.
Cinque is over rated and over run. If you could make it a day trip, get there, take a boat to see the towns from the boat. Get off and visit one if you wish and move on. We stayed in Monterosso once, but never again.
Milan is wonderful for 3-7 nights. See the Duomo, walk on its roof, go to its museum, go to Sforza Castle, visit its museum, if you can get tickets (from home) see the Last Supper, go to the Monumental Cemetery (unbelieveable!), one of their art museums, and on and on.
Lake Como, I don't have an opinion.
Venice maybe next trip. We stayed a month twice.
Lucerne is quaint but everything to do has to do with the boats. See Rigi, Pilatus, or boat to Fluelen and walk the Swiss Path to a location for the boat back. Otherwise, less time.
Lauterbrunnen, not Wengen. The most beautiful valley in the world. Been 6 times, never less than a week. Take day trips to other hiking such as First. So much here, I'll never get it in!
Skip Strasbourg. It's nice, not the greatest take, but not for one night. Heidelberg is better.
Maybe you have two trips here. Happy travels. Hope I helped.
