Never unless it is too far gone to rebuild after a bad crash. My 60 size Kaos is on it's forth rebuild and cover job right now. I have broken the fuse in half twice over the years. It's 12 years old and sees more stick time then any of my other planes. My CG Extra is about the same age, maybe a bit older? It had the nose of the fuse break in half and I did the repair on it and I'm still flying it. Both planes will go out with me tonight for an evening fly. These are kit built planes, not some ARF that was built without using any wood. They will go forever unless something really bad happens. They do get a little beat and require some new covering once in a while and minor repairs but they are worth it.