Start with the cycle, not the machine. When a load that used to finish in one run now needs another, the cause is often air moving more slowly than it did. The drum, the belt and the heating element may all be fine. The exhaust path is the part most owners never look at.
What you will notice first
Walk the room on a normal drying day. Check whether the laundry area feels warmer or more humid than it did before. Compare how warm the cabinet and the room feel with an earlier cycle. Look at the clothes at the end of a full run. Damp fabric in the middle of the load, after the full time has passed, points at the air path more than at the drum.
The lint screen is only the start
Clean the screen before each load, as the manual describes. A clean screen does not prove the duct is clear. Lint gets past the screen and collects in the exhaust hose, at the elbows and at the wall or floor connection. Pull the machine out far enough to see the back of the cabinet and the hose clamp. Lint dust around the seams tells you that lint is leaving the drum and settling inside the duct. Lint is combustible, so keep the area around the machine clear of stored items while it runs.
Trace the duct from the dryer to the outside
Follow the hose from the back of the dryer to the outdoor hood. Count the bends. More bends and a longer run mean more resistance, and the air slows at each one. Check that the hose is not crushed, kinked or pushed into a gap. Rigid metal duct generally holds airflow better than flexible foil or plastic, and a hose that sags can trap lint at its low point.
Confirm the outdoor flap opens
Go outside while the dryer runs. The flap on the exterior hood should lift freely with the air. If it stays closed or barely moves, the duct is restricted or the flap is stuck with lint or debris. Leaves and nests at the hood are common where the opening sits near plants or ground cover. Note what you find and whether it changes the next cycle.
Keep a short log
Write down the run time for a standard load, how the room feels, and the state of the outdoor flap. Repeat the check across the next several loads. A steady change over several weeks tells you more than one long cycle does, and the log is the record you will show whoever you call.
When to call
Cleaning the full duct is a job many owners hand to a service company, and that is a reasonable choice. Ask the company to clean the whole run from the dryer to the outdoor hood, not only the cabinet side. Ask what they will check at the outdoor flap, and whether they will record the duct length and the bend count in writing. If the dryer is already near the end of its planning window, the airflow check helps you decide whether a cleaning is worth the visit or whether the replacement date should move forward. Use the Clothes Dryer: typical service life and when to plan guide to place the install year on the calendar.