This may vary depending on your location, but in Wisconsin tonight is the premier of the film "The Return of the King". I've got a ticket to the first show (11:57pm), which will be shown on the "Ultra Screen" (which means that the screen is huge and the floors aren't as sticky).
I know someone who is leaving for the theatre at 4:00pm. That means they'll be spending almost 8 hours waiting, and another 3 hours and 20 minutes watching the actual film. I'll be arriving at about 9:30, and leaving the theatre at about 3:30 am.