I just changed the cabin filter of my daily driver for the first time in 7 years. I cut up an old furnace filter and put the media inside the old filter frames like Max suggested. Before that one the original was there for nearly 10 years. The AC works MUCH better with the new filter.
I have been much better changing the filter in my wife's 2012 OB 3.6R and still can tell when it needs replaced.