When I've got extra after planting out, I often plant them as a bunch in a corner. They grow on, and you end up with some mini leeks with which to impress the cook when there's a stir fry on the menu ...
If I use any of those later to fill in gaps or when more space becomes available after a few weeks, I find that they never really grow on as well as the ones first planted out. Maybe if you can spare them the space they would get going next March or April, but I just get them up and use them by then. Perhaps they would be more likely to send up a flower stalk too?