That logic might have worked better if irretrievably linked to "new shoes logic".
As for myself, I fish a until a tree wants it. I have only 3-4 flies that I have "fished to death". I keep those as curios. Unless something happens to my ability to concentrate on my casting at critical junctures, I anticipate that part of one fly box will last me a lifetime as a curio cabinet. Honest truth.
Ed