However, within those rules it is still possible to be holding multiple fast passes at the same time.
While this is a HOTLY

debated subject here in the DIS, I will point out that as a rule of thumb, fast passes will be accepted AFTER the return window has passed. If you receive a fast pass with a return time of say 11:15 - 12:15 you can NOT use it before 11:15, however you could return to the ride a 5:00 in the evening, and the fast pass will be accepted. On RARE occasions people have been turned away when using a fast pass in this fashion, but returning to the same ride a little bit later will pretty much always get you on.
Using this information to your advantage, it is possible to wander around the park in the early part of the day, riding what ever you find with a short stand by time,
and collecting fast passes as you can (remember your current pass shows what time your next one will be available), then using up the fast passes in the evening when the stand by lines are long.