These cartridges seem to wear out after two years, at most:
The handle becomes difficult to move, both left-to-right and up-and-down, with lubrication of the (obviously metal-on-plastic) shaft being unavailing.
Having devoted considerable time & attention to keeping this thing alive, there really aren’t any user-serviceable parts inside:
I think the sliding fit between the two ceramic blocks laps itself into a more perfect joint, to the extent it’s wrung together and can’t be moved. Even after filtering, our town-supplied water apperently has enough micro-fine grit for the purpose.
So I have another valve core for the collection …
On the upside, the improved spout bearing rings continue to work fine, although it’s only been five months.