I was sure there was a way of doing this, but I can't remember. Most of the time during the day I sleep a notebook, which is fine for periods of non-use here and there. When finishing for the night though on a Vista machine I hibernate - actually the auto-hibernate is fairly aggressively set on all my notebooks, so even if I leave it in immediate resume sleep it will hibernate after an hour or so. What it means is that if I'm working off batteries it doesn't end up even flatter the next day. It's been a while since I used an OS X notebook actually on the move on an all-day basis, but the Air is getting a workout in that role at the moment. I know OS X is capable of the same thing but usually only when the battery is on low charge. I notice on the Air the sleep uses up around 10% of a charge during an ~8-hour night and that is not great, especially on top of the mediocre battery life of the Air. Is there a way to set auto-hibernate-to-disk after a certain period of sleep? I know I can shut it down, and a de-hibernate pretty much takes the same amount of time as booting up, but I want my stuff to come up as they're left.