I think it's too short. There are many scenarios you can come up with, but the best one is if you have a big family. Everyone wants to watch the movie, but in today's busy world you all may not be able to sit at the same time and watch, and maybe not even in the same day.
I can't think of a good reason for the 30 days/24 hours scheme Apple has come up with. I mean, once you download it, their work is done. What's the difference to them of letting you have it 24 hours vs. 48 or 72 hours? It's not like they need it back to rent to someone else like a Blockbuster.
I suppose they want you to hurry up and rent another movie, but even that doesn't really make sense because they're letting you hold it to watch for 30 days. It's just so weird! I just can't figure out the business strategy. I would have loved to have been a fly on the wAll when they made of these rules.