I remember when we were younger (around 10 and 6) I would always clean Abby's room once it got to the point where we couldn't see the floor, let alone walk. She had a big white waterbed and I would start by taking everything off the floor and either putting it away or putting it on the bed as a staging place to be put away later. Needless to say there was always a huge mountain of crap on her bed until I got the place done. The floor would be clean, but seriously... a MOUNTAIN of stuff on the bed.
I only cleaned for her a couple times a year I would guess.... but when I did it was always an adventure.