I've never had to replace an air filter because it was clogged up with dirt and dust. I normally blow them out with compressed air once every two months or so and I can see some "stuff" coming out but nothing that would render them garbage. On a snow blower there isn't any...just a heater box...no air filter and never a problem. My blower (with HS50 engine) was made in '78 and runs like a champ...BTW.
I can say with confidence. I clean out my air filters bi-weekly. And so much dirt, dust, grass clippings, weed seeds, etc is in there that it's a noticeable difference in performance .. mower gets run 9hrs a day 5 days a week
Rigged up a snorkel for my "home maid brush mower" to try to keep it from getting clogged up and I will say it worked like a charm. I used a filter adapter from a bad carb and a three foot long piece of plastic electrical flex tubing. A couple of pieces of PVC pipe I had floating around and it was done.
Used it the past few days while clearing tall weeds and lite brush around the farm.