Craig,
That's the thing. Whenever Apple has switched chips (Motorola > PPC > Intel), the machines using the previous chips get dropped like steaming tubers. The articles I've read suggest Apple will continue to support their current Intel-based computers for about five more years, but I buy for the long term. I'm hoping for ten or more.
Mind you, I'm running an 11-year-old iMac that is two operating systems behind whatever the current OS is, so it's not essential to run the current OS, but that eventually bites you in the bum. Something you need or want to install or run eventually won't. I know, progress, but it contributes to the ever-growing e-waste problem.
Joe
I hear you, Joe (especially so, that last bit).
I'm not so sure about these continued support reports, though. Back in the PPC to Intel change, the OS change interval had managed to stretch to circa 2.5 years (according to Wikipedia, Tiger was released on April 29, 2005, with Leopard on October 26, 2007). Starting with El Capitan, it has been consistently every June (June bugs?), with the OS support dropping off when the latest macOS is past two major releases back. Going back to the Wiki, Leopard became unsupported as of June 23, 2011, just prior to the release of Lion (aka 'Mac OS X Bitey' (c)Joe P), with Leopard Safari support and iTunes support eventually terminated as of 2012. With hindsight, that probably wasn't so horrible for my late 2005 Power Mac G5, that is, until the browser eventually needed third-party fork injections, not to mention when the
'You can't have this' app update rejections started.
As I type this, I am sitting at my GF's late-2012 21.5" iMac, a lovely near silent thing with a quad-core CPU and the standard factory installed only 8GB of RAM. Apparently Catalina is the end of the road for this, however, I've been keeping her (it) on Mojave, as there are a few changes for the sake of change with Catalina that annoy (me, not her). Trouble is, Mojave security support will end before this year is out, and that for Catalina next year. Funny enough, next year will be 10 years of this machines existence, but here comes that CPU event horizon again, so we won't be buying Intel (at least not
new Intel) anytime soon (knock on silicon).
Craig