Except when the update brings some kind of massive change. RHEL 6->7, for example, was when systemd became the norm, and so right around the time our customers

Except when the update brings some kind of massive change. RHEL 6->7, for example, was when systemd became the norm, and so right around the time our customers started upgrading, I suddenly had the hot potato dropped into my lap of needing to convert 20 years' worth of our software's init.d scripts into systemd services.