Hmm, I guess the first time I got asked by my current live in boyfriend I was 17. I replied with "ask me in 10 years." The second time he asked I was 22, I said yes... but then we realized we had a long way left on school. He picked up a double major... I'm transferring to an MA program. It just seemed like we would be able to do it all better after we graduated... including the engagement. So we kind of back tracked and said " I know I want to marry you, but there is no point in having that title right now and being asked every few days when the date is."
So, yeah, we both expect to marry each other... but there is still asking left to be done. I don't push him or say anything simply because I want to see what he can come up with and I honestly want to be surprised by the event even though I won't be suprised by the outcome =)
But, I've seen people wait til they were 30+ to get engaged and it doesn't work and others do it when they're 18 and it works. As somone who has been with my bf since I was a teenager... we grew very differently than what I expected and I'm glad I didn't marry him when I was a teen, because while we were growing I had the room to become who I wanted to and know that I wasn't tied down or had obligations. I've told my boyfriend that I don't need the expiremental phase as long as he is willing to do the things I would do if I were single with me- such as go out and party once in a while, get a little wild, and spend time living in different places. I'm not particulary into dating a lot of men because I'm picky and honestly I have a wonderful thing going. I wish I had met him later in life because I think it would have made for a more well rounded relationship, but my current relationship with him is extremely fulfilling and I'm not willing to part with that.