Myself, I find that a dodgy autopilot that may (does) decide to go sleep itself and isn't coupled to any nav/gps, along with a radio stack that likes to listen to static at the slightest sign of precipitation combine to keep me awake for at least 50% of the cruise. As for the other 50% I would like to thank cessna for their seat design. Never could get comfortable and whenever my head flops against the cabin, the vibrations remind me of an old girlfriends special friend she kept in the bedside drawer.