RE: Welcome to Club SAITO !
I have a couple of plugs that are in a bag marking them as break in plugs. Maybe there is truth to the swarf thing, maybe not. Just something I've always been in the habit of doing. I"m sure there is plenty of metal being slung around as parts mate to each other, and then is blown out the exhaust. At one time, maybe this was just a thing to do. Nowadays, glow plugs are too expensive to be buying all time time, imo. I put the new plugs in an engine once it is on the model and is ready to go flying. If there is enough metal to stick to the element and fry a glow plug then I've probably saved the price of a glow plug over time. That would average out to about an hour or two of flying a Saito maybe?