My dad is a TCM (Traditional Chinese Medicine) doctor. He told me that every hour slept before 12AM count as 2 times as effective. I tried it out for a few month going to sleep around 8/9pm. I usually find myself waking up around 1am. super alert and energized for several hours where I will do a lot productive writing and creating till 5/6am. Then I'll sleep for 1 more hour. And for the rest of the day I'm totally energized with no afternoon dip. I do think our current sleeping patterns is a bit limiting.

Here is a TED talk that touch upon the subject as well:

http://www.ted.com/talks/jessa_gamble_how_to_sleep.html