Be worth knowing for those interested if the heating blankets need PSW 120v like electric blankets do.
Reminds me, itinerant1 explained how he uses a heater to warm up his batts before charging them in cold temps. So that means he has to not get the batts so low that they can't run the heater for long enough to warm the batts. You would need to work out the AH the heater would need next morning and be careful to not let the furnace run the batts down past that SOC overnight.
Nothing very complicated, but you would be stuck if you forgot.