Ok. So just collect eggs over the winter and maybe brood in the spring?
Or incubator them??
It is best if you only store eggs for about a week before you incubate them. Maybe up to two weeks. So collecting eggs all winter is not going to work particularly well.
If you use an incubator, it is best if all the eggs are hatching at the same time. So you might collect all eggs that get laid within a two week period, and put them in all at once. The eggs that were stored for less than one week will be most likely to hatch, but the eggs there were stored between one and two weeks will probably have quite a few hatch too.
If you want more ducklings than that, you can get more than one incubator. For most purposes, two is enough: the eggs can incubate in one, and hatch in the other, and you don't have the problems of ducklings making a sticky mess on eggs that still need a few more weeks of incubating.
With two incubators, it can work well to put in new eggs once a week. That way you do not store eggs for more than a week before they get incubated. Just mark the eggs so you can identify them again.
For each batch of eggs, about 3 days before they are due to hatch, move them to the second incubator.
Once the first eggs have hatched, clean up the mess in that second incubator, and you are ready to move in the eggs that need to hatch the next week.
You can keep that system going pretty much as long as the duck is laying eggs, or until you have as many ducklings as you want.
For raising the ducklings, newly-hatched ones should be in a brooder with no older ducklings. But once they are a bit older, you can mix some of the ages together, so you do not need one pen for every single week that you hatched ducklings. For example, ducklings that are two weeks and three weeks old can share a pen with no trouble, and they can continue to stay together as they grow up. I am not positive how many ages you can mix, but a bit of experimenting and watching will probably let you figure it out fairly quickly.