A dryer vent does not clog all at once. Lint builds up in the duct a little at a time, and the signs show up long before anyone notices a problem. Learn them now, while they are still easy to read.
What the dryer shows you
Watch the cycle length. A load that used to dry in a normal time and now runs longer, or needs an extra cycle, is the most common early sign. Feel the clothes at the end of the cycle. Clothes that come out hot and still damp point to air that is not leaving the drum fast enough.
Check the back of the cabinet and the top panel after a long cycle. Some warmth in those places is normal. Heat that makes the panel hard to touch is not, and it is a reason to look at the vent path that day. The clothes dryer guide on this site covers the typical service life and planning notes for the unit itself.
What the vent path shows you
With the power off, and the gas supply shut off if it is a gas unit, pull the dryer away from the wall. Look at the transition duct behind it. Lint that has built up at the bends or along the seams is the usual cause. Then go outside and look at the exterior hood. Run the dryer and see whether the flap opens fully. A flap that barely moves, or lint around its edge, means the run is restricted.
What to do with what you find
Clear what you can reach, and check the lint filter and the drum seal for lint as well. Then compare the cycle times you noted with the times you see after cleaning. If drying is still slow or the cabinet still runs hot, put the question to the dryer's service provider. Ask them to check the full duct length, the exterior hood, and the exhaust path for the run you have.
Keep the age of the unit in view as a planning input. A dryer that is clean and well vented still ages on its own timeline, and the vent check tells you how the unit is being used, not how much life it has left.