I recently found a clothes dryer exhaust booster at Home Depot. It is made by Deflect-o and costs $150. The package info states that it can significantly reduce drying time on runs over 12 feet. My laundry area is in the center of my home and the dryer vent has a run of about 20 feet. I have to take the duct apart piece by piece to clean it about once a year or the drying times really go up. I am thinking about trying the booster.