No doubt timing plays a role, Alex. Setting a sleep time and sticking to it is one of the top tips offered by sleep researchers. Of course, for night-shifters that might mean a godawful time. So for those lucky enough to work day jobs, picking a sleep time that coincides with the sun’s routine is smart. I can’t NOT wake up when the sun comes up, so if I don’t go to bed at a reasonable time, I’m simply screwed.