I found a great article written by the Rogue Mechanic. It’s all about high end parts and wether if they are worth it or not.
This is the assumption that high-end components, or even frame sets for that matter, are supposed to last forever (or at least a very long time). For the most part, this couldn’t be further from the truth. Components such as Shimano Dura Ace and Campagnolo Record do command a price that says that those said parts should +10K miles, and for the most part, they do. But a couple of points that I want to make clear is that that Dura Ace or Record Carbon rear derailleur that has +5k miles on it will not work like it did when it was new.