It all depends upon what the room back ground temperature is, if the viv's in the house then I expect the background ambient room temperature won't exactly be freezing, if the viv's in an unheated garage then obviously less so. Do you have a oil fired radiator or similar you can stick in the room if you're concerned it's to cold (how cold are you talking)
Always worth having a few spare bulbs, stats, mats etc in the draw, definately something I do.
Mine went for 2 days over the last weekend when my stat failed whilst i was away for the weekend. He didn't look happy and had not eaten a lot, but he didn't seem to bad. Heat went back on and he was loving it ( so much he fell asleep sunbathing!)