Ours are pretty gross at the moment. I'm unable to change them, and Denver just doesn't see the need.
Up until last week though, I was sleeping on top of the comforter under a blanket, so technically I've only been sleeping in mine for a week.
Denver's washed his once, but only because Devin slept with him one night, and got boogers and snot and drool all over them. Oh yeah, and poop when his diaper exploded.