I purchased a new battery and upgraded my Hard Drive two years ago, as it pretty much died (at least that's what the MacStore "Genius" said). I've since been able to access the old HD on a "sled" using it as an external HD. But the new one has several times the capacity and is, well, new.
The point is, my mid-2012 MacBook Pro is still up and running well. I keep it in good condition, and have upgraded two essential components with little trouble and expense.
I should be able to continue to use it but Apple no longer supports this device.
Same with my iPhone. It still works, and does what I need it to do (be a phone, text device, browser, camera, and iPod replacement). But, it will soon be obsolete, as I can no longer update the iOS and most apps will leave my version off their upgrades.
Seeing as these devices contain rare earth metals and take time and expertise to produce (thus the price), it seems extremely wasteful to leave them behind when they are still fully functional.
I get it, I get it, the tech advances quickly, and chips made now far surpass the processing power and capacity of former models. Still, it seems a shame to waste tech that could be updated.