[jlg23]

> If you keep a decent sleeping schedule

The natural shift of the sleep cycle towards later hours during puberty is exactly the topic.

I would consider myself to be the textbook example: zombiesque in school until 10am, now, 25 years later, I naturally wake up at 6am.

[Merem]

Is that actually a thing though? When I got my own TV, I usually went to bed at ~22:15 because that is when the first evening movie ended. And that was before and after puberty. Eventually, at age 17, I found something I really wanted to watch which aired from 22:00 to 0:00, so that's how long I stayed awake. It had nothing to do with my body. Similarly, talking with classmates, I noticed that girls went to bed earlier (like around 21:00) and that was most likely because there wasn't anything interesting for them to do at later hours, while we boys either watched TV or played games. Almost all the boys quit around 22:00 which would make it a very healthy 8 hour sleep until they got up again. And that is aside from being physically active during the day which makes sleeping in rather simple. Of course, if you sit on your bum all the day, sleeping in does become more difficult as there is little physical exhaustion.