Ok, I've thought about this, and honestly it would take some major getting used to, I probably would have a really hard time going to bed at 8. I tried last night and lay there from 8 until about 9:30 before actually falling asleep.
It just seems like you can go with less sleep, if you're waking up later-- example:
Lets say you need to be AT work at 10, so you get up at 9. You could go to bed at 3am, and still feel pretty ok at 9. 6 hours of sleep.
However, if you get up at 4-- if doesn't matter if you go to bed at 7, 8, 9, or 10-- you're always going to feel like death at 4. Although, maybe this is just me, and isn't the same for everyone else.