>I've had similar experience. How do you quench your gap?  Also, I've driven
my 12/60 neons at 140 v without ill effects.  Yet.  
>Suggestions from others?

my gaps are 14 copper tubes (12 gaps) no forced air...gonna do some new
ones, cause the tubes are mounted in a pvc pipe (sewer drain) and when they
heat up the plastic shrinks the gaps together. Prolly try forced air thru
the assembly to cool and quench.