Having your dryer vent inspected and cleaned often is very important.
If a vent gets clogged, the built up lint could become a fire hazard. The heat from the drying could cause the lint to combust igniting a fire in your dryer and home.
A clogged vent limits the air flow of your dryer reducing its ability to proper dry the contents of the dryer. This can cost more money in energy bills and also put greater strain on the dry having to work harder to get the job done.