Cast aluminum alloy wheels are on the Vstrom, which is a pretty popular bike for long distance touring. They hold up to hits very well, can't imagine hitting hard enough while touring to actually break them other than an outright crash.
A likely worst case scenario is hitting hard while your tires have low air pressure (for riding in sand) and you'll end up two nice flares in the outer edges of the rim. This may or may not have some impact on the ability of the tire to seat against these edges and therefore cause a small leak. This can be solved with a judicious use of plyers, or for the very brave, a visit to the local small bike repair shop who will happily pound your tires back into square with a mallet and and block of wood.