Quote (Serria @ 12 Feb 2015 16:46)
Literally as much as you need. But to be more scientific falling and rising with sun is probably the most sufficient way unless it varies a lot. Even then you can vary with it to an extend.
Of course it will adapt it's not like it has anything to say to our mindless sleep deficit trend.
The question was how much sleep do you need to avoid feeling tired
Not what is optimal for health and longevity.