On 9/1/16 we had our HVAC tech remove the humidistat from the wall of my home. While the tech was doing the work he told us he would connect the common wire to the thermostat and we would never need batteries again. Plus if the thermostat goes blank it indicates that the condensation line is clogged and the float switch has turned off the HVAC system.
We Suggest that when you have your yearly AC check ask your professional AC tech to see if you can change yours. All he needs to do is to see if he can connect the common wire to the thermostat. The good news is you will never need batteries in the thermostat again and have the added benefit of knowing that the condensation line is clogged and will be able to take corrective action.
We suggest replacing all smoke detectors and thermostat batteries at least once a year.