Dear LIB readers: Should I accept my boyfriend's promise ring?

From a female LIB reader

My boyfriend and I have been dating for seven years, since we were in the university. We are both 27 and although I am ready to settle down he says it's not something he is considering at the moment. But he promised he would marry me when he was ready and offered me a promise ring just last month. I refused to accept it as I see a promise ring as kindergarten. I would have preferred an engagement ring but he says he's not ready to be engaged either. Should I accept the ring and wait till he's ready to get married? What's even the symbol of a promise ring?