I'd be willing to bet that whoever did the repairs that you had fail probably did not know what the hell they were doing and did not take the time find out out how to PROPERLY do the repair-- or failed to take the time to do the steps needed to do it properly.
Yup. It's like writing a book: thinking up a story is easy, writing it is hard.
When dealing with shop stuff, proper implementation is essential no matter how good the idea.
It's why I don't recommend that pipe makers go the Delrin tenon route. Not because Delrin tenons can't be made to work---they definitely can---but because glued-in tenons lower both the skill set and financial barriers to entry in the carving game, so are commonly found on "beginner" pipes. Pipes made by people who don't understand what's required to make a solid join when a super-slippery material is involved, and so the joint frequently fails.
In short, the many Delrin screw-ups produced by beginning carvers has cast a shadow on the concept. It's similar to General Motors hastily modifying its 350 V8 gasoline engine to run on diesel fuel in the early 1980's to capitalize on diesel's dramatically lower pump price at the time, and doing it badly. The vast majority failed catastrophically in 30K miles or so. The result? It's been 30+ years, but diesel cars in the US are still viewed with suspicion by the general public. (The irony being, of course, that the most reliable and durable internal combustion engines on the planet are properly
executed diesels.)
