It all depends on their wing strength & how fat they get. I know my 3 month old drakes could fly if I didn't clip their wings & they came from a hatchery.
It will really depend on their size & wing strength. I would start out with clipped wings & just kinda watch from there to see if they are doing a lot of flapping & whether they can get their toes off the ground with clipped wings. As long as they can lift themselves with clipped wings I would...