That actually makes sense. I spoke with a Sig Sauer CS rep today who really knew his stuff and he mentioned that all handguns will eventually go. Even a P320 FCU which is just the metal insert.Just to be clear - frame or slide cracking is a grain structure issue, metal fatigue due to repeated use. It is NOT happening because the pistols are grinding themselves thinner and thinner until they’re too thin and finally crack.
However, as far as metal thinning out, if the metal doesn't fatigue and crack will the slide rails eventually thin out and fail, or they will crack from metal fatigue before they thin out? I've seen some photos of competition handguns with the slide rails pretty thinned down, but still functional.