Depends on riding conditions. Wet and or dusty less than 4000mi. Dry it'll last forever. Unlike your car the aixbox is inches from the ground and wheel, and it has about 1/10th the surface area of a car filter. One thing you can do if you get tired of buying $25 filters is cut out the paper filter from the plastic body and glue in K&N filter material, than just clean instead of replacing. It's about a $50 one time purchase.
