Please don't mess up the sheets unnecessarily. It's not very green.

You book a room, you check in. Those are the only requirements. It's none of the hotel's business what you do in the room, and whether you choose to sleep in it or not.

There is no need to physically check out. I rarely ever check out since hotels have been slipping receipts under the door. If it makes you feel better, call the hotel in the morning and ask them to check you out.