It's not about the three years you've already invested. It's about the fear of another year repeating itself until you die. Your doubts are a vital part of making your decision. Take them apart by figuring out what fuels them. Perhaps what you're seeing are larger trends in the existing cycles, but you can't describe them. A friend of mine once put it really well: it's not what you see in each other, but whether you are both looking in the same direction. from this perspective, it doesn't sound like you are. Think about a five-year plan with her. What milestones would you expect (buying a house, starting a family, feasting on the flesh of your rivals while drinking mead)? What would she expect? If you do not see enough overlap, you have an answer. Marriage is not always the next step. Don't let social expectations push you into a legal contract. That's like signing up for a cell phone plan because they let you call Denver.