Every person who joins through HivePostify stays on Hive.
Do they? I've delegated some RC, but you need to show results. Aiming for thousands of new users is worthy, but will not be easy. Keeping people on Hive is even harder as they need coaching to keep them on the right track. We have seen far too many give up or be driven away when they are thought to be abusing Hive.
I want to see more people enjoying Hive without being hassled, but I have no say over what others do.
Good luck.