The space under her bed where my roommate hides her mice is a bit of a cold spot. She turns the heater up to the highest setting while we’re out, so it doesn’t get too cold for them.
I think mice aren’t delicate little flowers, and that they should be fine under the bed in their shredded paper nest. She says that domestic mice have been bred apart from wild mice for over a hundred years, and that they’re not quite as hardy.
The reason it matters is because when the room is hot, it’s too hot. I prefer to use no heat at all during the winter, as the heat from the surrounding rooms more than makes up for any cold in here. When I come back from class at night, the room is like an oven. It’s not the worse inconvenience in the scheme of things, but if I don’t have to put up with it I’d like to know. (We’re keeping them there for a reason, so “Just move them elsewhere” isn’t good enough).
No need to guess how much colder it is down there.
Get a cheap thermometer and keep it right beside the mice. That’ll help her keep them in the recommended temperature range, regardless of what the thermostat says.
Heat rises. Make sure their cage doesn’t sit squarely on the floor. Also, beware of drafts. It may be stinkin’ hot up where you feel it, but it can be cool/cold and drafty under the bed.