不时之需

Explanation: From time to time: some time. Never know when you will need 　　Usage: Partial official; as object; that never know when you will need 　　Source: Su Song, "after the Red Cliff": "I have Doujiu, possession of quite some time, pending the child shall from time to time." 　　Examples: Have sufficient food reserves to be ~. Thesaurus:  have something ready just in case, Shall from time to time