After certain years - In Jehoshaphat’s 17th year 1 Kings 22:51, not less than 8 years after the marriage (marginal reference note).
Related Commentaries of 2 Chronicles 18:2
2 Chronicles 18:2
2 And aftera certain years he went down to Ahab to Samaria. And Ahab killed sheep and oxen for him in abundance, and for the people that he had with him, and persuaded him to go up with him to Ramothgilead.