Why would that hardware "have to be thrown away"? I've seen quite old GPUs still in use; given the current demand, I expect the vast majority of hardware used in these data centers to see a lot more extended use than most other types of electronics around the world (e.g. phones).
Oh, interesting - it's about failure rate following degradation after prolonged use. I didn't think of that - but my take is that if companies like Google are actually using those components until they 100% exhaust what the components are capable of, then we can argue about whether this use of resources is better than an alternative use of them, but it's by definition not a waste of resources.
