Well. Does anyone know when I should tell my man to stop?

He just loves to play with my boobs, it turns him on, and in turn, it turns me crazy also. I love it. But I have read and heard paying and suckling boobs can trigger contractions and labor. I am 24 weeks now, and it hasn't been any issue. Should I ask kim to not play at some point in pregnancy, or is this kind of a myth that it can bring on labor?