I'm sure someone will provide responses to the contrary, but hasn't Apple been pretty good about providing support for quite a reasonable period of time for both their software and hardware? Apple's own recent announcement indicates that they supported various bits of "vintage" hardware (hardware support only) that was first introduced between five and seven years ago: https://support.apple.com/en-us/HT201624
The same KB article indicates that what they consider to be obsolete (not at all supported) is hardware that is about 8 years or older, with most of it being 9+ years since first introduced.
The same KB article indicates that what they consider to be obsolete (not at all supported) is hardware that is about 8 years or older, with most of it being 9+ years since first introduced.