Cut the duct and install the booster
If it takes forever for your clothes to dry, the problem could be the dryer duct. A dryer vent duct that's too long reduces the airflow and wastes energy. Most dryer manufacturers recommend a maximum duct length of about 25 ft. But the catch is that every bend in the pipe is equivalent to about 5 ft. of straight pipe. It adds up quickly.
Dryer duct boosters can increase the airflow in a duct and help overcome this problem (search for “dryer duct booster” on the internet or check with appliance dealers). They switch on automatically when the dryer kicks on, using an electric fan to speed up the airflow through the duct, which increases air flow through the dryer.
Mount the booster to the wall or ceiling at least 10 ft. from the dryer and in the path of the existing vent. Connect the vent to the booster and plug it in.