10 day Santorini+Naxos+Athens in May 2023

I only see seven days accounted for. Do you have ten?
Book asap, I have a suspicion this will be a bustling year for tourism.

Looks like you have thought things out well. We assume you plan 3 nights in Athens at the end?

If you are really planning way ahead you might try to make hotel bookings for 2023 at the end of the 2022 season just before hotels close for the season. Chances are they may turn off their booking system and go into relax mode for the winter months.

Flights generally can be booked 11 months before the departure date. Start checking and watch for good deals and sales. Aegean will not have t her 2023 schedule ready to roll until late in the year so start checking for your flight to and from Santorini around November. They often have seat sales early in the year so watch for one of those.

As stanbr tell you, Aegean flight schedules in May 2023 will not be available in 2022.
If you plan to fly with Aegean, you could open an account on Aegean airline and subscribe to the special deals newsletter.
in February and March, there are often promotions valid for a few days that can go up to 50% for flights in spring or summer.

About the ferries.

Ferry timetables for May are generally available from mid-March.
(Today March 14, some timetables for May 2022 are not yet available and those published may still change)

For a ferry trip in May you can book your ticket a week in advance, that's more than enough. (my friends also used to traveling in Greece laugh at me when I book more than 2 days in advance, but like you I prefer to plan ahead)
You can find ferries schedules on websites such as:

https://www.ferryhopper.com/en/

or

https://gtp.gr/RoutesForm.asp

I too live in South Florida.

We went to Greece in 2018 and are returning this May.

Are you only going to be in Greece 8 nights? Really, it is far and a lot of trouble and expense to stay for that short of a time. You can’t get a direct flight from Miami to Athens so it will be three flights to get to Santorini. My first advice is find a way to have two more nights in Greece and then spend 3 nights in Athens in addition to the 3 on Santorini and 4 in Naxos. That still is short but doable in my view. My second advice is to fly from Naxos as opposed to the ferry to maximize your time in Athens.

As far as flights go, for both trips I saw cheaper fares in August for following May but wasn’t ready to pull the trigger. I don’t regret it as we made changes to our itinerary that made it better. But if you can have things figured out, you might be able to take advantage of that.

We bought in November of 2017 for May 2018 but our youngest son would not commit as he wanted to do an internship the next summer. That was sorted out in March and the price was not any different than what we had paid in November.

For this year’s trip we bought airline tickets in January. We were able to buy through United one ticket from Miami to Zurich to Crete. In 2018 we had a separate ticket to Santorini. But we were only able to buy on one ticket to Crete by finding flight first in goggle flights. So my third advice would be to use goggle flights to search and track prices but then buy on airline website.

Be aware that there are no direct flights between the islands.

If you want to go from island A to island B you will have to take the ferry.

By plane you have to take a flight from island A to Athens then Athens to island B, which will certainly be longer and more expensive.

Cautious travelers accustomed to ferry travel in the Greek islands avoid having a ferry ride the same day or 1 day before an unmissable flight, this because of the weather which can strongly modify or cancel ferries in the Aegean Sea. (in May it's quite rare because the Meltemi is not blowing yet but it can happen).
So if you can catch a flight to Athens instead of a ferry before returning home you will avoid this kind of inconvenience.

My recommendation would be to fly from Naxos to Athens. It is not uncommon to encounter a one day ferry strike in Greece which would leave you scrambling to find a last minute flight back to Athens in order to catch your return flight to Miami the following day. That happened to us and it was a level of stress that you don't need on vacation! We had registered our trip with STEP and they alerted us to the strike. Had it been left to the ferry company, we would not have known until we arrived at the port.

Thank you all so much for the great advice!!!