Even this is understating it; if you buy at the right point in the cycle, you can Ship-of-Theseus quite a while. An AM4 motherboard released in Feb 2017 with a Ryzen 1600X CPU, DDR4 memory and a GTX780 Ti would be a obsolete system by today's standards. Yet, that AM4 motherboard can be upgraded to run a Ryzen 5800X3D CPU, the same (or faster) DDR4 memory, and a RTX 5070Ti GPU and be very competitive with mid-tier 2026 systems containing all new components. Throughout all this, the case, PSU, cooling solution, storage could all be maintained, and only replaced when individual components fail.

I expect many users would be happy with the above final state through 2030, when the AM6 socket releases. That would be 13 years of service for that original motherboard, memory, case and ancillary components. This is an extreme case, you have to time the initial purchase perfectly, but it is possible.