I've never enjoyed sleep as much until I got the 'Today' job. There is something about early sleep that's much better than late sleep. I feel myself going to sleep; I don't just plonk my head on the pillow. It's a sort of winding-down thing.
Even though disciplined sleeping habits and the adrenalin of live radio ensures that we are very awake while on duty, there is evidence of a phenomenon called circadian desynchronosis which causes one's brain to function slowly at those times of day when it thinks it should be asleep, regardless how wide awake the body is.