>Lifetime
Hi
It's all depend on Brand, and quality of components.
My IBM PS/2 95 still run smoothly for 10 years without any problems. If you buy cheap Taiwan / China /HK PC, it will break down in 3 - 6 months!
Make sure the PC have adequate cooling. Leave several AT/PCI slot cover open. Installing additional fans and an external desk fan next to the computer is suitable for Tropical weather ./ Middle East. area
I have idea about replacing old motherboard in old PC AT cases with new Amiga One motherboard, unfortunately Amiga One does not support AT format.
Amiga One will be a great upgrade for old PC.