Swatcop, I would suggest that you look for a grounding problem, intermittant. That usually is the reason got the sensors going bad. The ground MUST be attached to the engine some place that it doesn't shake loose. On the C/H I attach the ground to the hex part of the sparkplug with a small hose clamp an in all my years of using C/H have never had a sensor burn out.
I think its a ground problem