Long dry times are the most common dryer complaint and the one most often caused by a hose crushed behind the cabinet. The lint screen can look clean while the run to the exterior is packed. Heat that cannot carry steam outside keeps tumbling a wet load and overheats the cabinet.
A burning smell ends the experiment. Pull the clothes and leave the dryer off.
Moisture has to leave the building
Clean the screen every load. Feel the hose between the dryer and the wall for kinks. Go outside and see whether the damper opens when the dryer runs. Lint mushrooms on the cap mean the run is shedding debris because it cannot flow.
Heat that never arrives
Cold tumbling is not a vent story. Electric dryers fail elements and thermal fuses; gas dryers fail igniters. Fuses often open because a vent was already restricted, so a heat-part replacement without a vent check is how the fuse opens again.
What not to open
The heater box and the gas burner chamber are not lint-screen cousins. If the accessible hose is clear, the flap moves, and the load is still slow or cold, that is a diagnosis with the cabinet open — on the correct heat system for gas or electric.