I remember the days I'd stay up till 10 and get up 7-7:30.  Now if I make it out 9-9:30 I'm doing good.  I never set an alarm anymore.  I automatically wake up by 6:30 at the latest.  Most times it's about 5:45, but on occasion it's 4:30.  Sometimes it's because I need the bathroom, other times I just wake up.  I figure after 4:30 it's not really worth trying to get back to sleep.  That's when I fall back to sleep at about 6 and sleep hard and not want to get up at 6:30.