Currently running a ThinkPad x380 with a 8th Gen intel quad core and 16gb of ram. A bit old by modern standards, but on Linux it’s plenty fast and I probably won’t have to upgrade for a decade. And that would only really be if the hardware was either worn out or there is some major upgrade I feel I need. I got it a few years old for $200 (it was a top spec model when new), I can fix most of the problems that might come up with it with used parts for cheap, and when I upgrade I’ll probably get another cheap laptop where running Linux won’t make it feel slow. From experience, if it were running windows it would begin to feel slower a lot sooner than with Linux, and indefinite security upgrades are not guaranteed.