That's what I noticed too. I assume that when I turn off the MBP, that it turns off or puts the mouse to sleep. I've had my Magic Mouse for about two weeks and haven't turned it off. It's at 87% right now.Well when I turn off/shut down my iMac for the night I notice that the light on the magic mouse goes off so I assume that shutting down the computer also shuts off the mouse. So considering that the little light under the mouse goes out I assume it's off. Does anyone disagree with this assessment and if so why? Thanks for any reply.