I let my Muscovy hen raise hers for 3-4 weeks. Once I took the babies away, she started laying about 2 weeks later. She was very unhappy and grouchy for a few days when I took them, but she got over it and started to build up her nesting spot again.
If you take them away right off, give her a week or two before expecting her to lay again. Plus it depends on the season and the weather where you live. I am in Maine and it's already down into the 30-40s at night. I have one hen left sitting on eggs (due in a week), but the rest of them stopped laying in September. If it gets cold where you are, she might not lay again until spring (depending on the breed of duck you are talking about too).