When I was in high school I needed at least 9 to 10 hours of sleep a night. If I didn't get that I was grouchy and unpleasant and generally miserable. As I progressed through University this got better and I was able to get by with less sleep. I never became happy with that though and would always enjoy it when I got more sleep. However lately, I've gotten to the point where I simply don't seem to need as much sleep at all. I regularly go to bed after midnight and I'm not grouchy for the most part or anything like that. I also find that if I try to go to bed earlier I either can't fall asleep right away or I wake up super early. I guess this is a good thing, but I find it a bit strange.