What maintenance does the dryer's exhaust vent system require?

Lint should be removed from the entire length of the exhaust vent system at least every 2 years, or more often depending on usage. You should also use no more than four 90° elbows in the vent system, use the shortest vent length possible, and replace plastic or foil vent material with 4-inch (102 mm) diameter heavy, rigid vent material. Service calls caused by improper venting are not covered by the warranty and will be paid by the customer. (Page 5)