> I always worry what do you do when your hardware fails

There is only one answer to your question: It is irrelevant.

Yubikeys are not that expensive, and anybody who depends on Yubikeys should have minimum two of them.

This isn't a Yubikey thing. Its a basic IT equipment redundancy 101 ... if its important, minimum N+1 it.

The same reason you don't put all your eggs on a single disk.

First: Always buy two (or n+1). Enroll both. Store one somewhere safe.

Anecdotally I have keys from 2013 that are still working fine when I test them, although they've been superseded by newer models.

To my knowledge no one has done the Consumer Reports / Mythbusters style of testing, buying many Yubikeys over time (to get different hardware batches) and subjecting them to various tests...

I used the same one for work every day from 2018 to 2025.