I'm another one with pets in the bed so how often I change the sheets depends on how much licking, shedding, barfing and wallowing they've done in the bed. Mine are Bostons and Bostons are "burrowers" - they insist on sleeping snuggled under the covers, not on top of the covers. And they've been known to sneak some of their favorite dirty spit-covered toys under there with them. So if they goober up the bed, I have to wash all of the bedding, not just the top layer.
