I am sending you an answer from our data base that gives some good suggestions. I referred to your profile and see that you have a Kenmore model 11086545 dryer.
The most likely cause of longer drying is airflow. If the hot air doesn't go out of the dryer properly it doesn't remove the moisture and the clothes don't get dry. Taking the vent hose off the dryer will eliminate any problem with the house vent. If the clothes dry faster with the vent disconnected your house vent is restricted. If they still don't dry properly there is something wrong with the dryer.
Look closely at your lint trap screen, sometimes the tiny holes get restricted with detergent and softening products. You can usually wash the screen with some detergent and clean it.
Check the top and sides of the dryer and see if they are getting hotter than they used to. This would indicate that the element is OK and there is an airflow problem.
With the vent removed and the dryer unplugged look into the pipe that the vent hose attaches to. Sometimes lint will build up in the blower and slow the airflow down.
Either thermostat can cause longer drying times. If the top and sides are getting extra hot the thermostats are probably good.
The element can also cause the problem, but the only way to be sure is to check the amp draw of the element and you probably need a technician to do that.