8, I have had two now, once with one of those little switches that come with a flight pack, that was 10 or 12 years ago on my scratch built 40 size Fokker. The other one was last week on my CG Extra and it was one of the JR super switches. It didn't go out, just had dirt and general crud from the lake bed in it. A few shots of QD electrical cleaner and it's working again but is now an on and off switch for one of my gassers ignition.
This is just a wild guess but I am betting K3 has never owned or operated a gasser. Probably half the guys I fly with have gassers too and none of us bother bringing out anything in the way of a lot of spare anything. None of my planes I have flying at the moment are heavy vibrators, gas or glow?? Maybe I'm just lucky??