[OAC_Sparky]

I do mine once a year, right after the winter. Unless your area is particularly dusty, you don't need to do it any more often than that. I put 35000Km on my car a year.

Partsource usually has thhe K&N Recharge kit on sale once every couple months. Follow the directions, let the filter dry overnight wrapped in a paper towel if you can. The biggest problem people cause themselves is by overoiling the filter and getting said oil in the MAF.