I got tired of swapping air filters on my 7120, two years ago.  Last year, I installed the Hillco before going to the field.  I still had the habit of checking the filters every morning.  I went thru all of the beans and part of the corn before blowing out the filters.  They probably could have made it thru harvest, but I felt I still had to blow them out.  My neighbor had the Hillco installed on his combine and asked me how many spare filters he needed to keep around.  I told him none, but to keep his best spare filter, just to have around.