I was able to get a fast pass in the early afternoon for a 6pm return, HOWEVER, after carefully planning my day so that I could make the American Idol finale that day, I ran to the fast pass line hoping to get through in under 25 minutes (which had never been a problem with a fast pass for me) but the CM said that the FAST PASS wait would be AT THE MINIMUM 40 MINUTES so I wasn't even able to use my fast pass that day because they closed the ride exactly when the finale was finished (when the park closed)!!!
He said it was because many people in line hadn't used their fast passes during the time they were supposed to so if you get a fast pass with a late return time, you may be stuck in line for much longer than you expected.