About 5 years ago, I brought a just bulletproofed 2007 F-250. It came with a new stock air filter element and after towing my 10,000# camper and running around for 38,000 miles I noticed that the air filter indicator only is showing 1 line of restriction. I know it matters how dirty the air going into the air intake is, but how long to these air filter elements last?

 

Depends on where you drive..
The dirtier the incoming air the sooner the filter will need replacement.
It is good that you keep an eye on the restriction indicator.
Many folks let more dirt in just opening up the filter housing to look at the filter than if they relied on the indicator alone.