It depends when you buy vs. when it was first released. The 2014 Mac Mini for example was sold until late 2018 so it's perfectly possible for someone to have bought it Sept. 2018 which means only 3 years of new macOS versions as it didn't get Ventura. I think the model with the best supported OS track record from Apple is still the Mac Plus from 1986 which was supported all the way through 7.5.5 in 1996.