Final answer:
Air filters in heaters and air conditioners should be replaced or cleaned as per the manufacturer's recommendations, rather than at specific mileage intervals.
Step-by-step explanation:
It is essential to replace or clean the air filters in your central heaters and air conditioners to maintain a healthy environment free of dust and other pollutants. While some may suggest that filters be replaced at certain mileage intervals, such as after every 12,000 miles or 15,000 miles, the most accurate guideline is according to the manufacturer's recommendations. These recommendations are made with the specific system's requirements in mind and will vary based on different factors, including the type of air filter and the environment in which it operates. Therefore, always refer to the guidelines provided by your system's manufacturer as the primary source of information for filter maintenance and replacement schedules.