Not always. At least half the time though. It's not in the middle of collecting mail from any server either. It will finally quit but after about 30 seconds to a minute. I usually just go into activity monitor and force quit it. Annoying as hell. There's not a lot of feedback on this issue as I'm guessing most just "sleep" their macs. I on the other hand sometimes shutdown to squeeze out every minute of battery when I'm on the road.