(More seriously, I suppose I really should do the prep and paintwork in advance of installing the new thermostats, but that requires detaching the original thermostats and leaving them off for a day while the paint dries. And when exactly are we going to have a day when the weather is so absolutely perfect that we need neither heating nor cooling for a day? Should I just hope there's some slack wire in the wall, pull everything out, and let the thermostat dangle from the wires?)