Unpopular opinion: Your deck is never done. Even excluding new sets bringing new cards that might be good in your deck, your meta is always evolving, you yourself as a player might be changing.
I doubt no matter how much you have improved the deck, gotten feedback and followed up on it, your deck will never truly be finished, unless you are fine with it not being the absolute "best" version of itself.
Obviously, once your deck is consistently playing well in games (25+% winrate, rarely gets mana screwed/flooded, etc.), then upgrading it becomes more of a want than a need, so you could call it finished then if that's good enough for you.