Certainly, as long as your discard has no mold on it and looks and smells healthy, it's still good to use, however, older discard has a much sourer flavor than a fresher, newer discard. I prefer to use aged discard in savory recipes like pasta or crackers, and newer, fresher discard in sweets recipes like brownies, cookies, and bread. I consider 7 days and less to be a newer discard and 7+ days older to be an aged discard.