I have heard a lot of people do not stay for the whole of their program and most people who do leave before the end of their program leave close to the beginning of the program. That being said, I do see it as selfish. The college program, generally, has "young adults" in it and those young adults need to realize that when they sign up for something they need to follow through with it, whether they like their job or are unhappy or whatever else. There's plenty of reasons to stay and the main one I can think of is that you said you would. When you pick your start date you say you will stay until your end date and leaving early is pulling out of that, which is why Disney makes it so hard to get accepted again because who knows, the person who left may leave again, possibly putting them in a tight spot when it comes to workers.