There are approximately 2,900 home clothes dryer fires reported each year and cause an estimated $35 million in property loss. Failure to clean the dryer is the leading cause of home clothes dryer fires. More of this type of fire occurs in the fall and winter months. Gas clothes dryers have an additional hazard in that a clogged vent can result in a release of potentially deadly carbon monoxide into the home.
You can either clean the vent yourself by buying something called an auger brush that attaches to your drill and can be purchased at a hardware store, or there are various companies who will come out for a reasonable fee.
The lint screen should also be cleaned after each load because the dryer will work more efficiently when it's not clogged and a buildup on it can eventually lead to possible fires as well.
If you want to save money you should dry loads back to back why the dryer is still warm. This results in a faster drying and less energy use.