Charlie's Kane heat mat has stopped working. I bought it at the end of 2016. Is it expected for them to stop working after so much time? I'm ready to buy another but before I do I have a question. Charlie is 22 years old and well over 100 pounds. I haven't measured him lately. My current mat is 18 x 28. He can't fit his entire body on it. His box is about 4 feet by 3 feet. Because of his size, he can't move off the mat entirely if he gets too warm but that has never seemed to be a problem. I don't lock him in at night so if he gets too warm, he can poke his head out. Would you get a larger mat, and if so, what size would you suggest? There is a RHP on the ceiling. It is keeping his house in the 70s at night, while the outside temps are in the 40s. The thermostat is set to 84F.