Bob,
Glow plugs are considered an expendible item in the world of Radio Control. They all need changing periodically and virtually everyone has spares available. I don't know what the average life is in a turbine or what the best type to use is. I have always had good luck with the OS series. I suggest you try the OS glw plugs and see if you don't get longer life out of them.

Regards,
doubledee