It would also fit nicely to the world as Skyrim is in the North, hence shorter days and longer nights. Also, from what we have heard from the new AI it shouldn't be to hard to implement.
http://en.wikipedia.org/wiki/Segmented_sleep
I'm not saying every NPC should do it, but the ones whose lifestyle it would fit.
Imagine spending a few days spying on NPCs to learn his habits before you rob his house empty OR risk him waking up and causing you to take measures. Run if he didn't see you. Talk your way out if you can. Kill him if you feel like it.
Anyone else hoping to see this in Skyrim?