Servo heat-sensors or paranoia?

I was adding to my E-stop circuit for my servo system on my mill, when I
came across a nice little item on the electronics site I use. It's a
small temperature sensitive switch that drops in resistance from 100Mohm
to 100 Ohm when a certain temperature is reached. Different models come
tuned to different temperatures.... Like 50 and 75 degrees centigrade.

Cut to the chase: Has anyone attached these to their servos/steppers and
wired the whole chebang up to an E-stop circuit? How common is servo
burnout (blunt tool/loss of lube causes the motor to run at way too much
power maybe?) Would anyone recommend this? Or is the likelyhood if this
kind of failure so small that it's no worth my while implementing?

Thanks!
~Abby