I lose a silly amount of battery life when the tablet is not in use.

Battery life isn't great when in use either.

Dell support wouldn't do an exchange because the diagnostic check came back fine.

They did tell me to turn down screen brightness etc., not very helpful because I've tried all that. Stayed on Dell's recommended settings trying to avoid this issue. My sleep study seems to indicate that the unit is rarely in sleep at all.

If a fresh install of windows doesn't fix this. I'm done. And dell support has been anything but actually supportive. If it doesn't fall in a checklist you are sol.