I was only able to persuade him the first time. Then I eventually gave him something. The second time there was no option to persuade, and when I just closed the dialogue, he left. Someone a while ago here on Lemmy posted a screenshot of a letter he will write to you before he leaves if you just ignore him. In the scope of the game, what he asks for is insignificant. When you don’t know about his limit, and he takes the first 3 magic items you find, it is a little painful.