When was the last time you had your dryer vent cleaned and inspected?
Removing all dust, lint and debris is a crappy job, but somebody has to do it. The key words here are 'somebody has to do it.' Because if you, or someone else doen't clean your vents periodically, you are taking a signifant risk.
Dryers are capable of generating very high temperatures to get your clothes dry. If the dryer exhaust pipe is choking off with lint and dust build-up, the heat cannot escape as it was designed to do. When the heat can't escape, it gets even hotter.
You hear about it all the time. How did the fire start? It started in the dryer. As a first responder in our local Fire Department I have seen the devastation first hand. Get those vents cleaned out folks!