No matter when you write it, it's always yours. And though we often think of these creations with affectation, taking them as our actual children, unlike real human children you can give birth to the same story more than once. One of my most favorite of books is A.C. Clarke's The City and the Stars. The story itself has a storied history, originally appearing as Against the Fall of Night, a novella in the November, 1948 issue of the magazine Startling Stories, it was revised and expanded in 1951 and published in book form in 1953 by Gnome Press. It was later expanded and revised again and published in 1956 as The City and the Stars. As long as you don't sign away the rights, you can take as many stabs at a story as you like. It's yours.