Electroair spark plugs

For those with an Electroair ignition using the Tempest UREM37HE...are you having short plug life due to internal shorting in the plug barrel? When my plugs fail, usually in less than 100 hr, I can see a black spot inside the ceramic barrel and the plug tests bad on the tester (appears to be shorting in the barrel). I wonder if the high voltage is too much for plugs basically designed for magnetos. For those using automotive plugs, are you having short plug life? Which particular plugs are you using? Thanks for any input.

I have 500 hours on mine thus far with no issues

I have about 450 hrs and no problem.

Thanks for feedback. My problem must be with the wire termination and those stick in springs...

That would be my suggestion. Replace the spring