[nostrademons]

I find my acceptable waking points occur in 1.5 hour sleep cycles, and how many I need depends on how mentally taxing the stuff I'm working on is. For ordinary work, stuff I know how to do fairly well already, I need 8 hours. If I'm learning something new or putting in long hours that require concentration, I'll need 9.5 hours. If I'm thrown into a completely new situation - say, I need to decide the architecture of my startup and learn 3-4 new frameworks all at once, or I've just moved cross-country and started a new job - I'll need 11 hours. I can also function on 6.5 hours but feel pretty crummy, and there's a noticeable performance penalty for anything that requires concentration (math, computer programming, etc). On 4 hours of sleep, I'm a zombie - I do okay with everyday tasks and social interaction (with people I know), but can't really learn anything new and retain it. Curiously, I feel better on 4 hours of sleep than on 6.5, 9.5, or 11 - I'm more alive and less groggy, I just notice that my performance on external measures declines.

I recall in the 2010 there were a bunch of athletes that all said the secret to their success - besides training hard - was getting 9 hours of sleep at night. IIRC both Sasha Cohen and Shaun White mentioned it.

I think I'd also read brain research that REM sleep (which tends to be back-loaded towards the end of the night) is when your brain converts experiences from that day from short-term memory into long-term skillsets. That'd be consistent with my experience that more mentally demanding tasks require more sleep, and the experience of those Olympic athletes, and that I don't really suffer a short-term penalty from lack of sleep, it's more a long-term problem.

[swah]

But how do you do this? You wake up and go to sleep again and again? I wake up naturally after 7 or 8 hours, would be kinda hard for me to sleep 11.5 hours.

[jarek]

I've never had problems sleeping up to 12 hours. Might be a personal thing, or related to whether you have accumulated sleep debt.

[nostrademons]

I find that I'll often come up to a point of half-consciousness at about 8/9.5/11 hours, but as long as I don't sit up or get out of bed or start checking my e-mail on my phone, it's pretty easy to fall back asleep.

Whether I want to depends on how much mental activity I've been doing; I'm far more likely to think "That was a nice dream, I don't wanna get out of bed yet" if I've got a thorny challenging problem in my head than if I'm like "Gotta get into work and start coding."

[sycren]

I think it also depends how much light you have in the room. I think you would find it easier to sleep longer if the room was still dark after 8 hours.