When you part with a male duck how long is before the female eggs are no longer fertile?

It varies among species of ducks. Some female species can store sperm for a week or less, while others can store sperm for 100 days or more. For those ducks storing for a week or less, pairs often continue to mate throughout follicle development. This ensures the female has sperm available to fertilize the eggs as they leave the ovaries and have viable eggs.