Mechanical keyboards should provide much less fatigue if you avoid "bottoming out", which is much easier to do when a key has lots of travel and a dampening force curve. Most people suffer fatigue from these very low travel Apple keyboards as fingers will come to an abrupt hard stop. It's almost like typing on a hard surface.

The Apple keyboards were designed to be thin at the expense of everything else, reliability, maintainence, longevity, and comfort.