How Long Can I Keep Using My Devices Before They Become Obsolete?

I'm curious about how much longer I can rely on my devices before they become obsolete or stop working altogether. I bought a MacBook Air new around 2020 and it's still running fine. Unfortunately, my 13 mini phone has a cracked back glass, and I'm returning it because it turned out to be a knockoff instead of an Apple housing. This leaves me with pretty much just a screen and logic board to work with, and I'm considering getting another mini.

I also have an iPhone 7 as a backup, which I'm currently using until I figure out what to do with the parts of the mini 13. What's the best solution here? I don't have a lot of money to spend, so I'd like to squeeze a bit more life out of my current devices. I'd hate to wake up one day and find out nothing works, which would just add to my hassle.