I have tried to look for this topic, sorry if a repeat. I have a large bunny and a large cat, thought a heat pad would be a good Chrissie idea. Do they work, the microwave ones I mean? Do they stay quite hot or just lukewarm. I tend not to have the heating on at night but have quite high in day as I have health problems. Will the pads keep them warmer? They seem quite small are they really worth it? Thanks.