Not just teen .....

http://news.bbc.co.uk/1/hi/health/6962085.stm

But, these days, generally, my body is taking care of the time I sleep. I know that it's best to have a fixed time for sleeping though. And that you need to be in the dark to ensure melatonin production so I'm getting enough sleep and probably going through the right stages of sleep now to produce new cells etc.