Dryer would not heat up; blow only air

I replaced the thermal cut off kit, and the dryer now had heat. Three days later, no heat; the thermal fuse also did not have continuity. Read on-line that overheating was the most likely cause. So, I checked the exhaust duct for blockage, but it was clear. Then, I removed the exhaust canister at the back of dryer; the entire bottom was filled with lint the size of a softball. The lint was heating up, and when it got too hot, it blew the thermal cut off. Cleaned out the lint, replaced the thermal cut off, and now it's fine. Moral of the story: Remove the lint canister and clean it.