Most spindles are asymmetrical yet it can be inverted if the chainrings don't hit the chainstays but that is usually impossible (I've done it on a road bike but with a single chain ring that i moved it on top of the spider rather than the original on the back of the spider.. not for wear but for a smaller chainline)

For distributing the wear on the spindle you can install the cranks in difference position related to the spindle (180 degrees)