In RAM trucks it can really restrict the air flow for your heater and A/C. Good practice to change it every time the engine air filter gets replaced. I’ve been pretty negligent with mine in the work truck though.
Depending on your truck, it may not even have one. One of my trucks just has a mark where you'd cut the plastic if you wanted to install one. Not surprising, after 155k miles, the air barely blows. No great way to fully clean a dirty evaporator on them, short of removing the dash.
First thing I do when I get a car, is carefully remove the cabin filter and carefully throw it in the garbage, then carefully put the cover back on. A/C always blows much harder for years to come. Problem solved!
