It depends how many FP tickets are available really - in really high peak season, FP tickets have run out before noon. We don't do a lot of FP rides, but do our share of BTM, Peter Pan and Buzz Lightyear with FP - and basically after your FP ride timeslot opens you can go back and get more FP if there are still some available, until they have run out or until the end of the park day.