[Boog]

I don't know what the suggested change interval is on these filters but I can tell you I go down a gravel driveway at work. The yard is all gravel so dust flys a lot and all that accumulates on the cowl gets pulled into the truck on startup. I changed my filters a few months ago and just now checked them and you wouldn't believe the amount of powdered dirt and sand that had accumulated. I bumped them to release the dirt and reinstalled. I'm sure they will need it again by the end of summer. Imagine all the dust and crap we have been breathing in our vehicles before these filters were installed.
You sure can tell when they start to plug up as the air flow falls off.
It's a shame someone hasn't come up with an addon type of filtration for people who would like to have this on their vehicles that didn't come with it.