Not religious, and therefore marriage is simply an economic move. I don't think marriage improves or solidifies a relationship. If anything, it introduces an uncomfortable sense of obligation that has potential to introduce dishonesty and bitterness into a relationship. I think all members of a relationship should ALWAYS be choosing to be together rather than staying together out of default or because they're just "used to it."
So if it makes sense to be a single financial unit, go for it, but go into it with a prenup detailing how you will handle a divorce. Because it's naive to go into any relationship assuming it will be forever. Best to always live in the moment and not make any concrete plans for a future that may not happen.
And in any case, whilst it's still illegal for same-sex couples to be married in most of the nation, I just don't want to support the legal institution of marriage at all. Marriage available to all or to none. Don't pick and choose.
I met my husband at an early age. I was 20. We didn't get married until I was 26. I always felt we "grew up" together. I also felt that if I had met him any later, things would have been different. I was a little more set in my ways and I looked at the world a bit differently. I really is up to the individual and personal circumstances.
I wished there was an answer--I don't think there is or should be a particular ideal age for marriage--it should be when both people are mature enough and ready and have met someone with whom they want to form a lasting commitment. For me, that wasn't until relatively late (that 35+ bucket), but I know lots of people including my parents that met in high school, married in their early 20's and have had long, satisfying marriages.
I met my ex-husband and married him at 20. The whole whirl wind romance thing. Now being divorced I have found plenty of hindsight to help me out. At 20 I knew what I wanted in a marriage and was willing to work for it but him, even at 29, he knew what he wanted. But he didnt know how to work for it and wasn't mature enough to try. That experience has taught me a lot about relationships. Even tho it ended in divorce I don't think I would trade it for anything because I did learn how to find what I want in a partner.