I definitely wouldn't put them in a garage. Even if it had great heating/ac there is so much air exchange when the door opens, not to mention all the fumes. I'm in IA and our basement doesn't drop below 60 on the really nasty -30 to -40 degree days. It usually sits at 65 in the winter. With the oil space heater in my snake room it stays 70-75, and there are two windows in that room. There's also no insulation and the outside walls are just cement blocks. An old farm house basement might be a little more sketchy.
As for the summer months the snake room sits at 75 and 80 on the nasty hot days. The flexwatt actually does heat up the room a bit because the rest of the basement stays at 70.