Repair of a leaky bathroom sink faucet; definition of "lifetime"

After 14 years, the hot side of the bathroom sink faucet was leaking badly around the stem, although it still worked fine otherwise (and did
not drip).
Finally got round to repairing it. It is made by American Standard, and appears to be 2904-line ("Williamsburg") or the like, which use Moen-style replaceable valve cartridges (the patent is long expired). For this faucet, the correct kit is item 028610-0070A "Cartridge Kit".
Installation was quite easy, but the suggested adjustable wrench is a bit clumsy to use because the hex flats are shallow. What works perfectly is a 22mm 12-point box-end wrench. Right-hand thread. One has to readjust the stop on one cartridge to allow the valve handles to line up correctly.
After finishing, I took the old hot-side cartridge down to the shop for an autopsy. The cause of death was that the hot water had over the years washed the grease out of the stem seal (two O-rings side by side), allowing the O-rings to wear and become loose. It is impossible to re-grease this seal without destructive disassembly of the cartridge, so one just replaces the cartridge, which costs $25 from the local plumbing supply house.
Now, this cartridge has quarter-turn ceramic-disk valve seats, and these show no signs of wear whatsoever. So all that advertising about the seats lasting a lifetime are true, albeit misleading - the cartridge will die far sooner. Not that $25 every ten years is so bad.
American Standard and others are now touting diamond-coated ceramic-disk valves as being even better, but I wonder if they solved the hot water washout problem. I guess I'll find out - I just received the new kitchen faucet, which has the diamond coated ceramic seats.
Joe Gwinn
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