29 y/o Kenmore 110 is blowing heater cut-off kits...

[MoTeD]

If you installed, on the first replacement, a 209°F, and the dryer calls for a 260°F then the tstat will pop again and again. Put the correct parts on and you should be good. Many of the other suggestions are great prevenative maintenance procedures, but should not be necessary. Ive been in the industry for over 10 years and never sold or replaced the gasket between blower housing and exhaust duct. Save the $26 and replace the rollers, belt and idler wheel with part # 4392065.  

[r_benner]

Thanks MoTeD. "Something" made the original kit to blow though. I Was hoping to find something obvious before I put another in.