Everyone's sleep requirements are different.
I know plenty of people that say as they have gotten older they are actually crankier if they sleep more than 5-6 hours in a night. Who knew?
I also know people like myself who seem to require about 9-10 hours in a night. Seems genetic, because my dad and his brother are (were) the same way.
Also everyone's schedules are different.
I never have to be at work before 10am, so staying up later and sleeping in is just fine for me. Sometimes when I say that I don't get up till 8:30-9:30am people look at me like I just grew two heads.
It's almost 1am here and I'm up on BYC
I used to work overnight shift, so I used to sleep really really weird times. Heck sometimes I would sleep whenever I could. Just catch a few hours here and there, whenever it was convenient. That sort of thing only worked for me in the summertime though. My body seemed to do fine if the sun was shining.
I sleep more in the winter because I don't want to get up while it's still frosty outside
Plus I can't seem to get up as easily without some good strong sunshine which is sorely lacking during the wintertime. I would probably hibernate if I could.
Edited to fix typo --- last time I checked it was impossible to sleep 90 hours in ONE night! lol