The answer to 'how often to replace thermostat' is that most thermostats last between 5-10 years with normal use. However, the lifespan can vary depending on the quality of the thermostat and how often it's used. Older mechanical thermostats may need to be replaced more frequently than newer digital models.
It's a good idea to keep an eye on your thermostat and replace it if you notice issues like inaccurate temperature readings, difficulty programming, or erratic behavior. Many homeowners choose to replace their thermostat every 5-7 years as a preventative measure, even if it's still functioning properly. This helps ensure your HVAC system is operating at peak efficiency.