Theoretically, an all-Plus network will be fine on its own without ever doing a repair. Here's a staff source:
But running one shouldn't hurt, and if you have "classic" devices on your network or ones that don't support NWI (network-wide inclusion...I think this is mandatory for Z-Wave Plus, but there's almost always something with Z-Wave that became required for certification just before or after they introduced new branding, and I don't remember if this was one of those things), you may need to when adding, removing, or physically moving devices.
