35000km of nearly all full speed Nordshleife miles. Remember this car is mostly driven flat-out by professionals and runs 500-550hp tunes. In an engine that wasn't brand new to begin with.
You are NOT putting anywhere near the same level of stress on your engine with the occasional trackday and canyon blast
I wonder if it would be more economical for them to do a rebuild at 25000km or so rather than keep buying new engines. Not sure if a rebuild helps when it's the block cracking though?