The problem here is the name…leftovers, who would eat them let alone enjoy them? Properly aged meals is a more accurate term. Who has not noticed that Chili, Brunswick stew, Irish stew and soups of every description always improve with age? These are the dishes that improve with age and there is very little doubt about it.
Even individual aged ingredients put together skillfully benefit from being aged. If it is yuck or yum depends entirely on the skill of the cook.