Angus,don’t worry about renewing the air filter every time.I purchased a new air filter in 2016 for my old K9 bike and simply wash it out with non-biological washing powder in the sink,rinse it well with warm water and simply let it dry naturally then store it the original box until the next time.We used to wash air filters from trucks the same way and they lasted years,plus remember trucks do a hell of a lot more mileage than our bikes do.