I stayed at pop century last year and they just started this new idea. Being a Disney guest gives you a few perks. On different nights of the week one of the Disney parks will stay open till 12 midnight. At 9pm all the other guest who are not staying with Disney are asked to leave. At around 8pm you will see queues forming around the park and arm bands being given out to the Disney guests. When you get to the front of the queue you show them the key that you use to get into your room and they will give you and your family their bands. I think the 2 main parks that do this are the magic kingdom and mgm which in my view are the best. Walking around the parks at 11pm at night is great. It lets you chill out in the day and go to your park at night, on some occasions we never went to the parks till after 8pm. We liked going to one park for 9am and left at around 12noon, we then relaxed by the pool for the rest of the day and then went to which ever park was open late. This is a great idea from Disney and it really works. Dont worry about getting back to your hotel as the Disney buses run till 1am.
Also at magic kingdom they have the night time parade and fireworks on at 9pm, whilst everyone else is watching this before they leave for the night go on the rides and enjoy yourself because they do it all again at 11pm. I do not know it you have seen this parade and firework display before but it is out of this world, not to be missed.
I hope I have helped.
Vinny
PS. I do not know if this is true, but I read on here somewhere that they were extending the hours by another 3 hours. I find this hard to believe but if it was, I would have been leaving at 2:45am.
P.P.S. You can come and go as you please in Disney. You could go in at 8am leave at 10am, go back at 3pm and leave again at 3:30pm and then go at night as well.