Cleaning the dryer lint trap. Really it's no big deal when you have nice place to throw away the lint when your reach out and grab it-so soft and fuzzy! It's usually just the lint of towels and cotton clothes that constantly fall apart.
The problem is that when a dryer runs, the moisture that get eliminated with the lint causing the dryer vent to get gummed up! Then the metal and plastic tubes leading to fresh air get full of lint as well. This makes a mess and in some cases leads to a fire inside the dryer vent cavity.
When I opened the back of the dryer up, I placed part of the diffuser on the floor.
If you've been cleaning the lint trap all along, but it takes longer to dry the clothes, the answer is deep inside the dryer.
Here is what a dryer looks like opened up like a factory repair.