Re: "Earlier this year it slashed the length of support perpetual licence holders could expect."
My Mid-2010 MacBook Pro got security updates for just over 10 years until they dropped support for High Sierra. I Hackintoshed Mojave on to it, so it is still getting updated that way.
The iPhone 5S (late 2013) is still getting security updates. Apple are a lot better than just about everyone else in that department.