Possibly longer than some stocks against which rich people take loans. Much stupider things have happened in the credit market.

Also, the Reuters article says that they have a depreciation schedule built into the contact. Compute hardware can depreciate pretty quickly, if I remember correctly major tech companies have around 3 years planned for the depreciation.

I expect they'll lose value in the step-function shape that's typical of technology, where each new generation decreases the value of the previous one. But that's fine, as long as each chip generates more revenue over its lifetime than it cost. And the lifetime can extend through multiple generations, as long as each successive generation is only a marginal improvement over its predecessor.

Personally I think the bigger risk is software innovations making CPU training (and/or inference) sufficiently viable that it's cheaper to train models on a commodity CPU cluster than on some proportionally expensive GPU cluster. I don't know enough about the space to say whether that's likely, but it seems like a low risk, since pretty much any parallel algorithm will always be faster on GPU than CPU - it's just a question of the marginal benefits and cost (e.g. maybe it takes more CPU to train same model in same time, but cost of CPU is so much lower that it's worth buying more of them).

Four years, maybe more. People aren't throwing away their A100s yet.

What value is good question.

But some value as long as computing power can be sold above running costs(power, cooling, etc.). Good question is when the newer model is so much more efficient it makes sense to replace them.

Once they stop working for training they can still do inference for a long time.