It's an inherently different thing. Fibre is infrastructure. It'll still function decades later. GPUs at this scale are consumables. I've heard 3-5 years lifespan before they fail out. This might be a low estimate, but even if you double it - they're 50% of the cost of datacenters. We're flushing entire countries worth of economic value down an Nvidia shaped toilet.

Anyone got any good testing data? Surely someone knows rough failure rate from constant usage?

It's not that they fail (which they also do), it's that they become obsolete. They consume more energy to do fewer operations relative to newer nodes. This is the basis behind Moore's law.

Ah gotcha, ya that will be interesting to see, but does seem like a more likely life of 7 to 10 years is possible.

I am curious on actual hardware failure rates due to heat etc.

I tried to do a calculation.

https://news.ycombinator.com/item?id=48762428

So 10% failure rate per gpu year. Some might be repairable and there might be a failure rate acceleration as time passes etc. So very approximate numbers.