Tbf batteries last quite a while...current ones maybe not 20 years of hard driving, but near-future battery tech seem like they'd be able to handle it.

I'd be more concerned about the underlying skateboard of the car; all the mechanical bits & bobs that are still required for an electric car i.e. the "car" part. I feel like new Chinese manufacturers' skateboard will be hugely inconsistent over time, whereas you find that consistency with established manufacturers - for example many EVs started out built on top of a manufacturer's existing platform.

That seems to be a myth. Real world data is showing most EV batteries are still in their first use (powering cars) at the 20 year mark. Once you have removed early model years of Nissan's Leaf and Tesla's everything before they began actively managing battery temperature (and removed the high totaled by accident rate of Teslas), EVs are generally lasting 15-20 years.

(The other direction: the costs of battery replacements haven't gone down because the demand mostly doesn't exist. The "range degradation" of EV batteries at 20 years isn't noticeable to the owners at 20 years.)