Dryer Taking Long Time to Dry Each Load? What Are The Warning Signs That You Need To Schedule A Dryer Duct Cleaning Service? 1. Clothing (especially jeans, blankets and towels) take longer time to dry. 2. Clothes are hotter than normal at the end of the cycle. 3. Outside vent hood does not move once the dryer is on. 4. The vent hasn't been thoroughly clean within the last year. 5. Dryer keeps shutting off before the end of the timer. 6. Noticeable lint accumulates behind the dryer.