Latest theory, it's been burning out (past few years) because the "starting temp" is set too high.
For example, if the fan starting temp is set at 90, then the operating environment will stay cool ~100-110, the motor will heat up, but only to <128C of the thermal fuse.
HOWEVER, if the fan starting temp is set at 110, That's different because then the operating temp will push the PEAK motor temp <at least for a little while> to a HIGHER rung, and on a particularly hot day, with a heatwave or whatever, Pooof, the fuse blows.