I've done this with all of the majors and have never had a problem. 90% of the time I do not even go to the room.

There is zero risk in doing this for a one night stay.

For a multinight stay, problems have arisen.

I did a two nighter at the IAD marriott. I checked in and went to the room just to kill time as I had a flight in a few hours. I did not do anything but sit in the chair and watch tv. I went on a flight and came back the next night to go to my room and actually use it. There was a do not disturb sign on my door and my key did not work. I kept trying till the guy opened the door and he said he had checked in that night.

I went to the front desk and they said that I had never checked in. I showed the my key package and the guy goes to the back room and says I don't know what happened.

I was billed for one nights stay. I argued this via the MR plat line and eventually got my two nights stay credit but it was a hassle.

All I can think of was that housekeeping said that no one was occupying my room. After one night, no biggie as you are supposed to check out anyway. For multi nights then the possibility exists that housekeeping can screw you over