How often should you change your air filter depends on what type of filter that you have in your home. There are several on the market. Some of them are one inch. Some of them are five inch. If you have the one inch filter in your home, typically these are replaced between 30 and 60 days. Sometimes more depending on how often your doors and windows are open inside your house.
Pet traffic, children coming and going will add to the amount of stuff that the filter collects. When it comes to the five inch filters, typically these last 10 to 12 months, again depending on the environment.