HAir filters are important to the health of your vehicle's engine, the air that flows into the engine goes through the air filter first and when your air filter is dirty or clogged that means that your engine is being starved for air. It should be changed before it ever gets to that point to keep your vehicle running at it's best. We advise for the engine air filter to be changed based on condition.
Some vehicles have a cabin air filter too, these filters are for the air that you breath in the car. We advise that your filter should be changed between 15,000 and 20,000 miles and some of that depends on the places that you go, if you smoke in your car then we advise it to be changed every 10,000 miles.