How often do Dryer Exhaust Vents need cleaning?

The better a dryer vent blows, the less lint builds up in it. Short vents blow better than long ones. Full size dryers blow better than smaller stack dryers or older dryers. Vents with a lot of turns and elbows blow worse and build up more lint. Very short vents attached to full size dryers may never need cleaning! Most vents, however, need cleaning every two to three years depending on the factors above.