Needless to say, I sure wouldn't even want a smart phone from 6 years ago. People get upset at the USA's more-or-less forced upgrades every 2ish years, but that cadence does seem to fit the timing of when I start to feel my phone is not up to par... 2 or 3 newer generations of devices have come out since my purchase, my battery is starting to lose life (usually never covered by any warranty as this is a standard "wear-n-tear" item like car tires). I'd think a 2 or 3 year warranty should suffice in most cases.

It isn't 6 years throughout the EU and for every product, though. The EU directive (= the text the EU writes that tells member countries what to achieve through their laws) states (paraphrasing a lot) that consumers may expect a device they buy to be what is advertised and to last as long as a typical device of what is advertised lasts (Business-to-business is different; there, it is more 'buyer beware')

As is typical for EU directives, that isn't very specific (partly for the better, as being specific would mean that such directives need to be revised all the time) and only describes a goal, not how to reach it.

Individual countries will vary in how they translate that into law. Apparently, Norway went for a very strong consumer protection.