What one can take the most damageare plastic glasses tight?
Both plastic and metal will last a long time if you're reasonably careful with them. But say once in a while you're not. The plastic ones will snap, and that's it. Replacement is necessary. The metal ones can snap (and may be solder-able or not, depending on where the metal separates) but more often bend. An optician can often straighten them so they sit straight and fit you again. So if you suspect your glasses are going to be prone to damage, get metal frames.
