My dryer is 1.5 years old. I have to run dryer 3x to get clothes to dry. I usually run it on medium heat/ energy preferred and my clothes dry fine. Lately I have to run dryer 3x @ 40 min intervals. My dryer has a sensor which is supposed to detect when clothes are dry and shut off (energy preferred, so it does not over dry clothes). The dryer does seem to get hot though, so I am confused why this is happening. 
I turned it up to high heat, seems to work a little better but still not how it used to.
It sounds like you have a clogged vent to the outside. Your dryer is too young to have any real problems. Tom ApplianceEducator.com