Check a Vented Dryer's Exhaust Duct and Outdoor Outlet
If vented drying takes longer, inspect accessible ducting and the outdoor vent, not just the lint filter.
A vented dryer needs an unobstructed path outdoors. The U.S. Fire Administration identifies lack of cleaning as a leading dryer-fire factor. This applies to outdoor-vented models, not ventless heat-pump or condenser dryers, which follow their own manuals.