> 2. It's not reasonable to expect to use it for 10 years. Even if Apple stops supporting it, you can still use it. In addition, Macs have insane resale value. So you can sell it in 5 years, and then buy a new one. This is a more reasonable approach than yours.
Why is that? I still use my 2015 15" MacBook Pro which released 7 years ago, and I have no intention of replacing it anytime soon. This isn't the 70s, 80s, 90s or early 2000s: the improvements in performance from one year to the next are far more modest and the utility of further improvements are far less impactful than they once were. My 2015 MBP is still as capable of browsing the web, writing code, and video editing as it was back in 2016 when I got it. It's not in any way slow doing any of those tasks.
The performance of an M2 MacBook would undoubtedly be much better, but am I actually going to be able to browse the web faster or write code any faster? Probably not.
A new 16-inch MacBook Pro with 1TB storage emits approximately 620kg of CO2e in its manufacturing process (The Carbon Footprint of Everything by Mike Berners-Lee, 2020 second edition, page 140). Why should someone emit more than half a ton of CO2e for a new laptop unless they really need it?
If you have a Mac that no longer gets OS updates by Apple, as long as it was released within the past decade you should be able to use OpenCore Legacy Patcher to update it to macOS Monterey (and later Ventura when it releases) without much issue. If it's older than that, you might run into some issues, but generally speaking everything from late 2008 and beyond is supported, with everything from late 2012 and beyond being fully supported.
https://dortania.github.io/OpenCore-Legacy-Patcher/START.htm...