There is no set answer for this. In reality, you might never feel like settling down and being exclusive with this partner, or even any partner. You don't need to be married to be happy or fulfilled. My own experience is that it varies with you, the person, and where you are in life. As I got older (and had more less than stellar experiences), I started to realize that I was a lot (a lot) more willing to accept less than perfection from a partner, and I began to value things like consistency, loyalty, and sincerity more than I did in my twenties and early 30s. I have been with the same lady now for over 16 years, and we are very, very happy. Don't push something, or try to put something abstract on a concrete schedule. The one piece of advice is that staying with someone when you are uncertain has an opportunity cost associated with it because you are forgoing the chance to date/meet other people. It is much easier to find a partner when you are younger than when you are in your 40s and 50s.