Originally Posted by
noglider
I've read reports from a few people that thin aluminum fenders didn't last long, but as [MENTION=73614]rhm[/MENTION] points out, most (or perhaps all) of these failures are from mishaps.
Not all are from mishaps; thin metal fenders (both aluminum and steel) also have a tendency to break at attachment points. Vibrations cause metal fatigue around the points of attachment, and as a result cracks propagate from the attachment holes. One can mitigate this with correct installation, which involves leather washers to dampen the vibrations around the points where the cracks would begin.