I recomend using o.s plugs. if your burning out plugs, it must be because they are getting to hot. from running too lean most likely. like the other guys said. that is the onhlythign i ahve had kill a glow plug on me. i find the o.s. plugs to be Extremely durable. i recomend the O.S. #8 for cooler weather, the O.S. A5 for warmer weather, and the O.S. R5 if your really going to lean it out. i have never used one of the R5 plugs, but i hear they are really good, and can survive really lean needle settings. Duratrax also akes really good glow plugs too. they have a medium, the carbon. And a cold, the gold plug. my dad is runnig the carbon plugs in his and they are really good. hasnt burned one out yet and they help hold a good tune.
for the os plugs:
http://www.osengines.com/accys/glowplugs.html
Duratrax carbon:
http://www3.towerhobbies.com/cgi-bin...?&I=LXAAX2&P=7
Duratrax gold:
http://www3.towerhobbies.com/cgi-bin...?&I=LXABK8&P=7