My truck is about halfway through its life, our winter road salt will eventually rot out the chassis. I installed a restriction gauge when I bought the truck. To date there is no observable restriction in the filter since the gauge has not moved at all. I have tested the gauge to ensure it is accurate. Anyway I decided to replace the filter after eight years of service. I dont expect to ever have to replace this second filter. Here is the restriction gauge Old filter Clean intake post filter The filter could have served for a few more years but I decided to splurge and change the filter. BTW the most recent UOA showed low silicon, so the filter was still doing its job well. Air filters are changed much too frequently, wasting resources.