Brightness does not mean anything if the fiber is broken. Most sights are fine as long as you are just shooting your bow. They are made for that. As we all know, sometimes things happen that you did not plan, like falling down on your sight or dropping your bow out of a tree. These things can ruin a hunt if your equipment fails.
Some materials hold up to abuse better than others.
Aluminum will bend, but can be straightened. Plastics with screws holding it will break at the screw holes. There is not much of a fix for that. Use only fast set epoxy or instant glue if you are trying to do some field repairs on plastic parts. Chemical bond glues, like model airplane type glues, will break down most of the plastics used in sights.