Having handled everything unruly from monitor lizards to birds and fish I know the feeling to wanna leave well enough alone if they don't want to be handled... I've been bit by more animals then I have shaken hands with humans I think. And they may very well never get used to it completely but at least you'll be able to tell when something happens. And ducks live around a decade... Believe me... At some point in the next decade you'll be glad you handled your ducks regularly. :3