Sang Zan calls Zhu Jiu a monster, and Zhu Jiu replies with that remark as a way of saying "fuck you". Given that Zhu Jiu reaches for that rebuke so easily, it implies that he finds staying in a cave for a century without dying to be abnormal, so Dixingians' lifespans would have to be less than a century (unless interfered with). Otherwise Zhu Jiu would find Sang Zan's lifespan just business as usual and he'd reach for something else to yell as a heated rebuke to Sang Zan's accusations of him being a monster.