Donaire should continue to work harder, if he have train hard in his previous fight, he has to double it as Inoue as a monster is a different animal.
It's good that Donaire fought other boxers previously before having a rematch with Naoya Inoue. In that way, he can test if he can still be as conditioned as he should be whenever he is fighting. No choice but to train wise and hard as Inoue is on a different level compared to his previous fights.
Still, an impressive TKO in both of his previous fights was established by Donaire defying the laws of age. He just needs to maintain that good condition as even how good Inoue is, there's always a thing called a turning point that can change the expected result of the fight.