Hi,
I don't know if it would be helpful to anyone, but I'm going to Italy in mid-September. I decided to buy a Firenze card for my 4 nights in Florence (September 14-18). I just made my Accademia and Uffizi reservations yesterday and it was just in the nick of time. Luckily, they still had 1 opening in each time frame for each museum that I wanted.
I was a little surprised that it was that close to filling up for my dates and times two months away.
It also took me 3 tries to get through to reservations. The first two times my call got disconnected. The third time was a charm!
I just thought I would post this in case anyone else is waiting to book their reservations :)