IMO if you're finishing up college or if you have just finished college, it's marginally ok. But one should try to get away from their parents right after finishing highschool if anyhow possible. While I don't mind people living with their parents (which happens especially in higher poverty environments), staying with the can have serious repercussions on your psyche and development as an individual. In most cases kids don't agree with their parents with everything (in some cases they are in almost nothing) so staying with them will only cause stress. Other than people often lack a sense of independence which is also not good for the development as a person. While it's nice to have things done for you, you can't learn to appreciate the small things in life if you have stuff given to you or done for you.
I remember how I went away from home when I was 15. I was in a nearby city, going to school and living with a friend in an apartment which our parents paid for. We would come home for the weekend, but over the week we were in the other city going to school. While this is somewhat intense (heck, leaving home with 15, think about it), it was not bad. Sure, our parents paid for it and we had some allowance per week to spend, but that was it. We had to do everything else ourselves. We had to clean, cook, take out the trash, buy groceries, wake up in the morning (obviously using an alarm) and get to school in time. There was even other stuff, but I won't go into detail. This was one of the best things that happened to me. I was taught independence and responsibility at a young age. It not only helped me immensely later in life, it also gave me much more confidence in myself and my abilities. I might not be where I am right now if not for those 3 years. IMO this was an important part in my maturing process. The difference between a person who's never experienced that and one who has is huge.
The 4th year of school I was actually back at home and I went with a car to school every day (an about 20 minutes ride). While not as mind expanding as the previous 3 years, it was definitely something to go with a car to school. That taught me even more responsibility.
So basically, I believe that people shouldn't live with their parents too long as it will limit them immensely. During schooling is ok, but one should become their own person. I think this is one of the biggest problems in today's society. Most kids are taught the values and beliefs from, let's say, 50 years ago and so they end up immature, needy, irresponsible, etc. It is directly reflected in the number of divorces today compared to 50 years ago. Of course, people staying with their parents is not the only reason for that, the reason is (as I already said) that people aren't being taught the right things. But by staying with one's parents, they also never get the opportunity to learn it by themselves.