I'm not certain it's the longevity of the actual hardware so much as there is a huge incentive to replace your hardware with faster, more capable equipment. Who wants to invest in the AI company that's using 10 year old GPUs when the next company is using brand new?
Old GPUs today are selling and renting for more than they were new which suggests the typical depreciation pattern isn’t holding.
There’s a risk that likely will happen that once demand is met capacity will overshoot significantly. However, when will that occur is very up in the air. Everyone is training every larger models and there’s more AI usage than ever