I view glass as a renewable resource! I'm on my third glass boat now and I normally don't do anything to them until the chines need repair. I have never had a problem with the bottom, but the chines will chip and break up after you hit a few hundred rocks. Bondo is a quick fix but will break out. For trips in very low water where chine damage is probable, I carry duct tape to get me out.
All of the above aside, glass is comfortable, quiet and can take a good beating. When major chine repair comes due, I go to the man who made the boat. Hope this helps.