Maybe most people are not capable of understanding the possibilities of a strong AI? It's not like we will just have a nice sounding personal assistant.
But they'll pump us full of anti-aging meds that restore us to youth, so they can work us to the brink of death again. It's more efficient than growing new humans through that whole irritating "childhood" phase.
They would have to repair us so heavily and so frequently that they would basically just be growing new humans, one piece at a time. I'd put my money on maturation tanks. Humans are finite and fragile, and will always lose to thermodynamics, eventually :-P
Certainly not infinite. There is and always will be a finite amount of computational power; considering thermodynamics alone, we can't continue to increase power usage exponentially or the surface of the earth will be uninhabitable in 200 years.
We used to call that „slavery”. There’s ethical considerations to AI, and treating it as a potential source „free labour” is one of the reasons I believe humanity shouldn’t be allowed to play with matches.
