The air filter media can last up to 6 months. It may be necessary to change the media more frequently, in the presence of high concentration of dust and/or particulates, or if the furnace fan is running continuously.In any application, the life of the media is dependant upon the total volume of air being moved through it as well as the amount of particulate it is filtering. Inspect your air filter on a monthly basis for cleanliness.
Honeywell F100F1012 Filter Cabinets
General Air Filter Media Part # GFGA100A29