Ok. Then I am sorry for understanding it that way.
But you *do* run new kernels, right? I think where I am left behind is the focus on init stability where that has to mean years of essentially not being touched at all while other essential parts are allowed to change in non-fundamental ways.
Note that for now I strive to avoid running systemd on essential systems as well as long as it doesn't mean significantly diverting from what the distro I have to use normally uses (and tests for) or what the local admins know well. Both has a higher chance of causing critical problems in my experience... But thats because it is - like btrfs - "fundamentally new" and not yet "incrementally new".