Remember the craze around the Titanic movie? That film ended up grossing like 2 billion worldwide. That's a crapload of money, and the funny thing is: a significant part of that revenue was made from people seeing the film multiple times in the theater.
Have you ever watched a film at the cinema a second time, or even a third? And then proceeded to buy the DVD, to watch that over and over again?
The film I've probably watched most is The Lord of the Rings (all three of them). Saw that trilogy three times at the theater (once back-to-back in an all-night marathon). When the DVD came out, I got it and watched it again like 3-4 times. Then the Extended Cut DVD appeared, and I watched that another 3 times. All in all, I've seen the complete trilogy upward of 10 times.
Star Wars is another trilogy I've seen a load of times (sadly, I wasn't born yet when the original debuted on the big screen), in various forms (VHS, DVD). When the high-def remasters come out, undoubtedly I'll purchase those as well.
All this pales in comparison to my little nephew, though, who watched Speed 40-50 times. Pure madness.