Mazuka, when is your trip? If you will be in florence for summer hours, when the museums are open all day, then the least crowded time to visit the Uffizi gallery is around noon, when tourists are having lunch. We tried this and it was nice, not crowded. We still had reservations for noon just in case. There was a line, though it wasn't too long, but we were glad to be able to skip the line with reservations.

If you can't get the reservations over the phone, you can have your hotel make the reservations for you. Ask them by e-mail if you have trouble with the phone method. Our hotel, Hotel Silla in florence, offered to make the museum reservations for us, a complimentary service. They sent us our reservation numbers by e-mail. It was very convenient.

The Accademia works well with a late afternoon reservation. It's not as crowded then (make sure you have enough time before closing.) We didn't spend more than 1 hour in the Accademia, the biggest attraction is Michelangelo's David.

Of course with advance reserations you don't go to the same window, you go to the reservations window. Ask if you don't see it. It should have the shortest line, if any.

We spent about 2 hours in the Uffizi Gallery. 2 or 3 hours is plenty of time for the Uffizi gallery.