WHY SHOULD I HAVE MY DRYERS DUCT CLEANED, IT'S BEEN WORKING FOR 20 YEARS!
If this is your question there's a good chance you have a disconnection hidden inside your wall which if left undiagnosed over a long period of time will cause mold and mildew buildup inside your walls. You could also be in a building with multiple units and a system that communicates with your neighbours. You're all drying into each others dryer's and you don't even know it. That's why some people complain and others don't. A dryer's flow takes the easiest path of resistance so if you're in a building with more than one condo its something to take into consideration.