You should always change your oil and air filter regularly for maximum vehicle longevity. While most air filters are not all that big, if you figure they are rated to last 15,000 miles, within 10 years, most drivers have thrown out enough of these to fill up a large garden-sized garbage bag. That's a lot of trash! You can replace all those air filters with just one if you purchase a lifetime, washable air filter. These cost twice as much as a paper filter (although they should last the life of the vehicle) and you will need to purchase a special oil to reactivate the filter after washing, but most people with reasonable mechanical ability should have no problem with such maintenance.