I’ve been researching Mac upgrades for a friend. Nothing quite like having to do niche research with two other people! Thankfully, since its a production environment, that simplifies things.
Depending on what you’re doing with Macs, you kind of have to decide if you’re going to try keeping up with Apple and your other software vendors or when you want to essentially crystalize yourself in amber. Either way you have a lifespan, but it changes between when Apple decides to finally drop support for you (technical obsolescence) versus no longer being able to do the work (functional obsolescence).
The nice thing is that with Boot Camp and Parallels, its easier to sidestep the issue slightly. If you have to, you can always turn the Mac into a Windows machine. Microsoft and its customers want long term support, hardware-wise, so there’s a degree of security in that regard.
Sadly, Linux won’t suit this particular group. But, hey, Linux isn’t for everyone.