If you're talking about a home lab or workstation environment I would 100% back everything up and start from a clean system. Go back to FreeBSD 9 or 10, in-pla

If you're talking about a home lab or workstation environment I would 100% back everything up and start from a clean system. Go back to FreeBSD 9 or 10, in-place upgrades have consistently bit me in the ass. Installer getting wedged, problems upgrading the boot loader, disk labels, freebsd-update getting wedged, you name it. If you're talking about a production environment, ideally your machines are more-or-less immutable anyways in which case you wouldn't be upgrading in place anyhow.