Dragon Ball Super has finally reached the milestone of Goku achieved Perfected Ultra Instinct. Goku finally managed to master that godly state of battle in order to defeat Moro, the evil sorcerer who's threatened the universe in Dragon Ball Super's latest manga arc. The road to reaching the complete form of Ultra Instinct has been one of the longest (and strangest) build-ups in Dragon Ball history: Goku got the power-up, then lost it, and fans had to wait more than a year to see it again. Now that Goku has seemingly stabilized his Ultra Instinct transformation, can we trust that it will last?
It seems that this new level of god-like power-ups brought about by Dragon Ball Super requires a different set of rules than the Super Saiyan transformations of Dragon Ball Z. It's somewhat understandable: In his Perfected Ultra Instinct state, Goku seems to be the most unstoppable mortal in existence - possibly a threat to the gods themselves. It's getting hard to find opponents that both have a reason to exist on the mortal plane, and can stand toe-to-toe with an opponent of Goku's power level. That's all to say: with Ultra Instinct on the table, it seems like Dragon Ball is quickly running out of ways to create compelling battles for Goku.
On the other hand, Ultra Instinct has been said to be a state that the gods themselves struggle to achieve and maintain. That detail of this strange new power seems all but rigged to allow Akira Toriyama to put the brakes on Ultra Instinct whenever he wants. Unlike Super Saiyan, Ultra Instinct isn't a transformation that Goku can just effortlessly tap into after breaking the barrier: it's a zen-like mindstate applied to god-level powers. It all depends on the situation.
The first time that Goku achieved Perfected Ultra Instinct, it was out of desperation to defend his universe from extinction; this second time he achieved it to honor the sacrifice of his friend and mentor, the angel Merus. It seems to take very extreme emotional circumstances for Goku to find the clarity and focus he needs for Ultra Instinct. That's all to say: there are no guarantees that Goku will maintain Ultra Instinct after his battle with Moro.
Question is: What would fans have the bigger issue with: an overpowered Ultra Instinct Goku? Or an ultimate power that gets trotted out and then retired as the series most 'Dues Ex Machina' gimmick yet? Dragon Ball has some fun choices to make, going forward...