I received my Z in September and installed a K&N filter in October. The air filter box looked pretty clean (fall was just beginning). From November to present I've only added about 500 miles and when I went to take out my air filter box (I installed an Injen CAI) I was shocked at the amount of leaves stuck in there.

It never dawned on me to check this box regularly. If you have a K&N filter it is easy to get complacent because you will go many miles before you have to take it out to clean.

Just thought I'd pass this experience along.