That sounds like a good idea. Like have the option for the player to shutdown after a certain period of time, or after you music has stopped playing. I think both options should be made available. But then again when you are not using your player it's not that hard to just shut it down yourself... My Studio V does have this feature though so if I was to forget or fall asleep with it on it will shutdown after 2 minute of being idle.
I have personally experienced the exasperation, on numerous occasions, of my J3 running itself dead-as-a-housebrick during work, and finding I cannot listen to it on the commute home. That's bad enough on a $300 DAP, but I'm not going to put up with this on an $800 DAP.
(JFYI, the J3 'auto-sleep' function was never properly implemented by the Cowon engineers - the player has a 40+hr battery life, but can kill it's own battery within just a few hours by going into some kind of infinite-loop or whatever, when it erratically fails to put itself automatically into sleep mode. Really, REALLY irritating after a hard days work and the prospect of a noisy, crowded train ride home! My DX100 is supposed to be an upgrade to my J3, so I can leave the J3 in my past. I don't want history repeating itself with the DX100, but it's looking worryingly likely if the above feature isn't implemented by iBasso's engineers. With such appalling battery life, iBasso really do have an obligation to ensure they at least implement robust power management features, and Android should offer quite a bit of flexibility in this regard)