The average dryer cycle lasts around 45 minutes, so if your loads require longer or you have to put the timer on a second time, the vents are likely clogged.
To properly clean it, unplug the appliance, disconnect the duct behind the dryer, and use a vacuum to suck up all the lint at the entrance to both the duct and the exhaust.
Many smart dryers alert users to clean the lint trap. Though it should be done after each load, it's best to check the vent if this alert comes up more frequently.
While checking the vent, empty the lint trap and ensure there are no bends or kinks in the duct, which can create a clog or error code. If the codes persist, get professional help.
Clogged lint traps and dryer vents are hazardous and can be flammable. If you smell something burning while the dryer is on, it's time to check the machine.
Open the cabinet protecting the fittings and remove the drum. Then, with your vacuum, clear out the drum, lint trap hole, and rollers, which are located under your dryer drum.