Haha...I've been feeling this lately myself.
Back in the day, every weekend or chance we got (we being my friends and me) we'd be out doing something stupid, staying up to watch movies and get drunk or nerding out playing some RTS all night long.
Nowadays I'm in bed by 10-11pm at night, up at 6:30-7am...and on the weekends, I can't seem to stay up past 12-1am...and then I'm awake no later than 10am. I used to stay up until 7-8am and sleep until the evening and wake up.
I suppose it's not ENTIRELY a bad thing. I just realize I cherish my sleeping much more...and I realize that if I don't sleep I'm an arsehole the next day and I hate life.