I have a 9 speed X01 that has I don't know how many miles on it but the jockey wheels are pretty much worn smooth. Still works just as good as new, which is to say it punts the chain between the cassette and spokes regularly.<should be in the what's right thread>
Fairly sure the X01 11 speed rear that's currently on my fat bike is now 9 years old, it spent about 8 years on my trail bike before its current home.
</should be in the what's right thread>