The answer to 'when to service thermostat' is that you should have your thermostat serviced at least once a year, typically in the spring or fall before the peak heating or cooling season. Regular thermostat maintenance helps ensure it's functioning properly and your HVAC system is running efficiently.
During a thermostat service, an HVAC technician will clean the unit, check the batteries, calibrate the temperature settings, and inspect for any issues that could affect its performance. They may also recommend upgrading to a programmable or smart thermostat to improve your home's energy efficiency.