But all that is just because computers are not designed for longevity, they are designed for capability. We could easily design them for longevity if we wanted

But all that is just because computers are not designed for longevity, they are designed for capability. We could easily design them for longevity if we wanted to: lower the clock speed so that passive cooling is all that's needed. Make all the PC traces five times fatter than they need to be. Use non-electrolytic capacitors. The resulting computer would be big and slow but it would last forever. In fact, it would not surprise me a bit if you could run a Raspberry Pi Zero for 100 years.