What would be the lowest that you would set the thermostat for while you're at work or at night? I've been reading different articles about conserving heat and they all suggest 55-60 at night and while we're gone. That seems too cold for the cats. We've got plenty of blankets and beds for them to snuggle up on but I don't want them to be uncomfortable. Right now we have it set at 65 when we're not there/night and 68 when we're home. If 55-60 isn't too cold, is it going to make them sick to have such a large fluctuation in temperature? TIA!