You are shopping for a clothes dryer. Hopefully it will best appliance you get in years. Did you know that this terrific time saver causes 10 deaths and more than 15,000 fires per year in the US? Yikes.
Kidde, the fire safety products company, put together a web site that has some good tips to prevent fires caused by dryers. firefyi.org
Some of the things they recommend are cleaning the lint screen after EVERY use and clean the vent and exhaust duct regularly. They do not say how often to do so but 1-2 times a year would make sense.