Once you start watching a movie that you rent from iTunes, you have 24 hours to complete your viewing of the movie. But there is a way to extend the 24 hour time limit. If the movie is playing, you can pause the movie and restart it even after the 24 hour time limit has elapsed. Once you close the movie, it will be gone. But so long as the movie is opened within the 24 hour time limit, you can pause it for as long as you like and then complete watching it.