I have discovered multiple times now that when I'm packing up to leave the office that I put my SP3 to sleep. Probably at least 3 times with the type cover closed method and 3 times with the power button and I put my SP3 in my bag or put it away only to return hours later from commuting or back to use my SP3 and low and behold it was not asleep at all. twice I have found it heating up my bag - doesn't get hotter than 80C so I don't think that it is over heating but the fan has no wear to exhaust so the body is warm. The other times is out on a table in sleep mode (or so I thought) only to find that the battery has drained. So in both cases the bad part is that I am expecting to have quite a bit of battery remaining only to find it in critical status. I suspect it is all of the applications I leave open. IE, Outlook, Chrome, Powerpoint, Excel etc. but that's the reason for sleep vs. shutdown anyway - so I can pick up where I left off. I have caught myself a few times pushing my SP3 in to my bag and clicking the pen and most likely waking up OneNote.