Update: found 3 dryers this month with lint packed so tight it was solid, and every owner said the same thing
I pulled the back off a 6 year old dryer in Mesa last Tuesday and the lint had baked into a hard sheet you could snap like a cracker, which is what finally killed the thermal fuse. All 3 owners in the last month swore they clean the filter after every load, but nobody ever pulls the filter housing out to check the duct behind it, and that is where the real clog lives. How often do you all take the whole duct apart on a service call, or do you just vacuum what you can reach and move on?