H.S.
HomeSafe Vent Cleaning does free video inspections of your vents so you can see if it is lint build up or a bird nest and the do a great job cleaning it out with a rotary brush and vacuum. Usually if your dryer takes a long time to dry that is the problem, especially if your dryer is not near an exterior wall because that means the vent is probably long and has some bends in it... sometimes they even exit through the attic.
Call HomeSafe and have them do a video inspection. ###-###-####
www.HomeSafeVentCleaning.com