I believe the pursuit of perfection is, and should be, endless, but in terms of an artist's craft, not a particular piece. Ideally, a piece reaches a finite point where it is fully "realized," for lack of a better word, where any further changes become almost arbitrary, or even detract from the quality. If such is not the case, then what's to stop an artist from working on a piece indefinitely?
Perhaps "realized" simply means you keep improving the piece until it gains the specific approval you seek for it, whether it be approval from a general audience, or a critic, or a peer, or an institution --- in my case I seek approval from a reputable journal (and subsequently, with any luck, readers of that journal). Submitting the story according to my method, then, the story's development will end when it is published, i.e. when the progressively decreasing prominence of the journals I submit to intersects with the increasing quality of the story.
Still, it would be nice to think my story could be realized without the approval of a journal, that its development will reach some natural endpoint on its own. Next time I review my beloved epilogue (and I really do love it), whether it be published or not, I hope I come away thinking: "Wow, this doesn't really need much change at all. It's great the way it is. Good for me."