No, he’s asking what you think a reasonable support timeline is. An open source project supporting hardware 6 years old is pretty awesome.
NixOS is an open source project that runs great on my 2013 Dell laptop. I think the real point of distinction is that brew depends on Apple's OS and SDK, which somewhat ties their hands, while other OSs don't.
6 years is really not a long time at all. You can probably find heaps of open source software out there that compiles and runs perfectly on 20 year old PCs. It's not like the maintainer has to do much to retain support--they just have to not make the software dependent on new operating systems.
Bits don't rot.