The other benefit of keeping the filters is that it keeps the AC coil from trapping dirt, in most cars the AC coil is the source of sour odors, black mold, name it...and the ones I've dismantled building race cars were always full of guk (Technical term
) so theres one benefit of running them.
And I get mine for 20 bucks at the dealer not 40..... Maybe its a local thing.... But they are available online for the best cost. Mine are still good after about 1.5 years so far...
Dave