How often do 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.
Are dirty vents a fire hazard?
A plugged vent will certainly cause a dryer to run hotter and increase the chance that something could catch fire. A dirty vent, however, is only one link in a chain of events that must occur for a fire to start.
Does it cost me money to have dirty vents?
Dirty vents can cause your dryer to take up to 10% longer to dry your clothes costing you more in utility bills every year.