I change my engine air filters at every oil change. That usually falls between 10-15k miles depending on the type of work I do with the truck within a given interval. The air filters are relatively inexpensive and a key to efficient operation with these trucks so I feel like it’s a small amount of money well spent. The last few times I’ve pulled the filter out, there was a fair amount of fine road debris, insects, dust, leaves, etc in there that I thought it best to change it. I’m at approximately 11k miles on my current service interval and I’ve noticed my truck seems to build soot a little more quickly than when the filter was newly inserted. Passive regeneration doesn’t seem to be happening as efficiently either. My suspicion is that the air filter is getting dirty again and may need changed. There’s a noticeable difference between when the air filter is brand new, and when it has accumulated mileage.