I've bent several, but never broken an axle.
Stainless isn't the strongest steel and also can risk galling on the threads.
I don't know if these are "fool proof""
Wheels Manufacturing Hub Axles

I just installed one a couple months back, but haven't had reason to pull the wheel and inspect.
I've also installed a fatter tire to help absorb some of the shocks the entire wheel assembly gets, including the axle.
This is on my "grocery getter" Rockhopper that carries 310 lbs. when I have a heavy grocery load. (solid axle)