Manufacturers recommend once a year for each part of your system. For your AC, preferably March - September is best because that's when the temperature is high enough to properly test. And for your heating, September - March to accurately test. Routine maintenance is sometimes required in order to keep your unit under warranty.
This kind of routine maintenance mitigates the risk of larger, more expensive repairs and keeps your system running efficiently. We offer a bi-annual maintenance plan where we service your heating and cooling systems once a year.