RE: Killing glow plugs by stopping engine with exhaust.....
Usually, I just let the vehicle runn out of fuel, but when I have to stop it, I plug the exhaust. Never had a glow-plug fail from that myself, but it isn't a common thing I do.
Most glow-plug failures I've had were either during break-in or if I accidently ran things too lean. "Age" fo course also factors into it, but once the engine is broken in, I find they last a long time.