Keep a thing seven years and you'll find a use for it
Keep a thing seven years and you'll (always) find a use for it.
Prov. If you keep a seemingly useless thing for seven years, you will supposedly have some occasion to use it during that time. Jill: My mother sent me a four-foot-tall ceramic vase for my birthday. What can I possibly use it for? Jane: Keep it seven years and you'll find some use for it.