I have to clean mine once a day, especially after mowing. I know it's plugged when it's 100 degrees out and it starts to blow warm air. I always carry a spare with me and just swap it out, when I get back to the shop, I blow them both out and ready to go for the next day. I also engineered a 2" tube that I inserted in one of the vents to bring air down to the floor of the cab, circulates the air a bit better.