That's kind of interesting, David. It made me think about the number of plane irons I've worn out. I can think of only one, and that is the iron from what was my first purchased plane, a brand new Stanley or Record no 4. As I recall, I bought the plane in the late 1960s or early 1970s, and the iron was worn out towards the end of the 1980s - my boss at the time said he's buy it for me which I suppose was unexpected enough for it to stick in my mind. I didn't see any need to celebrate, but I was pleased to retain functionality. I still own that plane, but since the early 1990s it hasn't been used anywhere near as intensively as it was in its first couple of decades and there's still quite a bit of meat left on the replacement iron which, by a rough count, must be close to 32 years old. I put that longevity discrepancy down to the fact that towards the end of the 1980s and into the late 1990s I acquired three more smoothing planes, all better performing than my old original plane which has sort of been relegated to occasional use, I suppose, whereas before it was my one and only smoothing plane.
I may have worn out one or two more plane irons, but I don't remember, and that may be because if I did get replacement irons the cost came out of my own pocket, something I'd perhaps prefer to forget, ha ha. Slainte.