> If mobile devices would routinely last twenty years, which they very well could, that would reduce a lot of e-waste.

Unfortunately, battery technology doesn't - and even if we had long lasting batteries, we'd also need fall-resistant screens. And no matter what, even if you have a device held together by screws and allowing easy repair instead of messing around with glue and click-tabs... screens still are really expensive, making it often enough more worthwhile to take the opportunity and upgrade the whole device rather than to repair the screen.

Batteries are easily replacable. LCD can last a long time, my main desktop monitor is 18 years old at this point. OLED less so, admittedly.