I have this on my bed and heat it up before I get in, and it feels SO cozy to climb into! I put the mat on the mattress, with a folded blanket on top of the mat, and then the bottom sheet over that. I leave it on all night but turn the heat down to 42. Even though I’ve only been using it a couple of weeks now, I think it’s helping to correct a very long-standing problem I’ve had with my SI joint. And I have to mention the fantastic customer service: there was a problem with my first controller, and when I contacted them, I had a new one in 2 days.