I’ve practised this while I was on V4 and the only trick was if you wanted to update the symbol, you had to delete every instance of it in the schematics and save the project. This caused the symbol to be removed from the -cache.lib and you could then insert updated version of it. Of course you could not have old and updated version present at the same time.
I don’t know how I’ll make my projects portable under V5, so any ideas are welcome.