Factors to consider when choosing how frequently to change an air filter: Where you live: You can extend the life of your air filter by a few extra months if you use it for fewer than five hours per day. Season: During the busiest summer and winter months, filters that generally last 90 days should be changed every 30 days. Your home's size: A larger home typically needs more frequent filter changes during heating service in Lexington, KY, because furnaces and air conditioners have to release more air to compensate for temperature changes. Allergies: You must change your air filter every 30-45 days if you have allergies. Family and pets: Families with children should replace their filters every 60 to 90 days, while households with pets should up the frequency to every 60 days for a single pet and every 30 days for two. Air quality: You will need to change your air filters more frequently if the air quality in your home isn't excellent. Southern Comfort Heating & Cooling can help you with all your HVAC services.