How long should you wait?

I've been in a relationship for 7 years and there's not ever been any mention of marriage unless it comes from me. He has known from day 1 that my intentions in any relationship was for marriage. I am 47 yers old and have never been married. He is 58 yrs old and has been married once. When I bring up marriage if I ask him if he wants to be married again he says it would be fine but hes okay with not being married as well. We've had our fair share of ups and downs but for the most part our relationship has been positive. I try not to bring it up too often because I don't want to be a nag. I just know I'm beginning to get impatient after 7 yrs together and I want to fulfillment dream of being married. I love him with my entire heart and don't want to be without him but at the same time my desires to be married are important to me as well. I don't want to give him an ultimatum as I know those usually don't end well. What do I do? Which way to I turn? I'm horrible with words and don't know how or what to say to him.