[RedDevil]

I agree that (Model S) pack failed. It wasn't a chemistry related problem though.
I was actually referring to the Model X pack, as it stood out against the other Model X-es in their fleet.
I liked that link as it was no typical Tesla fan brouhaha. It pointed out what went wrong and what went right. It is a pity to take a onesided view from such balanced reporting.

The point I'm making is that these failures have nothing to do with longevity or reliability.
A faulty assembly was faulty from day 1. It only became apparent later. But it is not a situation that would occur in anything but a small minority of packs.

The fact that there's no way to test for age on new batteries does not mean there's nothing that can be said about it. Average Tesla pack degradation seems to reduce rather than accelerate over time. So it is fair to expect degradation will not dramatically increase any time soon.

I maintain that todays battery technology has reached a level of reliability that ensures most EV buyers will never have to swap the battery.