Bo is 16 now and he seems to be cold all the time. He isn't as fat as he used to be (he lost weight when he had hyperthyroid, he's gained back some but is still thin) and he sleeps on the heater vent or under the covers with me.

I want to get him a plug-in heated bed. Does anyone use one, and what brands/types do you recommend? Are they safe to leave plugged in all the time?