I have a Centrino laptop from 2004, and it's single core, with 1.5GB RAM and, of course, spinning rust.

It works, but even playing a video on youtube can be taxing. I'm not arguing for "performance" tasks here, just sitting on the couch and surfing, and clicking random links.

Then again my home server is a 2013 i5 that does everything it needs to do (except be super power efficient). So I'd say ~10-14 years is the sweet spot, but 20 is historic and mostly useless, sadly