My husband and I got married when I was 22 and he was 23. We lived together about 10 months before we got married but had been best friends for about four years before that.
I think living together helped prepare us for marriage. I'm really messy, so he got to see if he could deal with the hurricane I leave everywhere I go. He has a short fuse and leaves clothes everywhere, so I got to see if I could tolerate that. If everything had been thrown on me right after getting married I probably would have felt like I got duped.
Even with living together, we were both on better behavior for the first two years together than we are now (at five years). I joke with him that I still got duped because I dated this nice guy who brought me presents for no reason and was super sweet and ended up married to someone I have to basically buy my own presents with and remind to play nice. That's an exaggeration of course, but you get the point.
I'm glad we got married when we did and I'm glad we lived together before we got married. Wouldn't change a thing if I could do it over.