Question: I have heard, but been unable to confirm either way, that double/triple wall stove pipe insulation breaks down with time. Further, after it breaks down to certain level, that the pipe is no longer safe and should be replaced. Can you answer this one way or the other? Answer: Although it is surely possible, the safety margin that is built into the pipe means that there has not been a lot of field failures of this type. Any type of chimney can fail for many reasons, including excess salt in the air, settling of insulation, cracking of clay tiles (masonry chimneys), etc.It is my opinion that if any of these instances were epidemic, there would be notices from the makers and/or the consumer products safety commission. I don't think that there are any notices of this type. Yes, some chimneys are better than others, but I would assume that most currently manufacturers double wall chimney are sufficient for their intended use.