It is very split. It also depends on other management techniques. I've only fed medicated feed once in my life. And that's a long life raising many thousands of chicks.
Most people prefer not to feed amprolium to ducks. If you can keep the bedding dry, (perhaps impossible with ducks) your chicks won't need medicated feed.
Are your flocks separate?
Too much thiamine blocker (medicated feed) can be harmful to ducks.
Raise them separately, keep the chick bedding...