We have been to Florence and the Academia. It is not very big, and an hour would be more than sufficient to see it. Also, everything is very close together in Florence. We actually booked at the Uffizi Gallery for our cruise in July. I booked for 12:30, as that gives us time before and after, and we can easily see other sights if it is too early.
There is a very good web site run by the Florence museums at www.firenzemusei.it
that gives opening times, prices, etc. It also gives the phone numbers to book at the museums themselves, without paying the exhorbitant prices some independent ticketing sites charge. The museums only seem to charge Euro 1.55 over the regular ticket price, and you do not pay until you arrive and get your ticket. Ask for an english operator. The call is very fast, and so not expensive even though long distance to Italy.
Hope this helps!