I don't know how long they stay with their parents in the wild but I have hand-raised ducklings and have also had a chicken raise a duckling. With the hand-rasied ones they went outside into a heated coop at 2 weeks of age. They were very keen on human company till they were about 5 or 6 weeks old, and then they stopped yelling out for me everytime they caught a glimpse of me going out the back door. They became more independent after that.
With the duckling that was raised by a chicken, he hung around with her till he was about 8 weeks old and then started to look longingly at the adult ducks. I think he suddenly realised that he was more like them than his foster mother. At that point he went to his new home where he now happily lives with a ducky girlfriend and an adoring family of humans.
But if you have only 1 duckling it will never stop being depenedent on you for company and affection. Do you just have the one? If so, is there any chance of getting a ducky friend?