Marriage is about two things, I’d say: (1) complete dedication to your best and leading partner in life, in other words mutual fulfillment of each of your highest aspirations, talents, traits & ideals – and (2) raising kids – and NOT necessarily in that order!!!
In other words, if you can make it together through all the trials & tribulations that go with the rewards of child-rearing, then everybody will benefit: the kids, and each of you.
The really important thing is to ask yourself: What DONT I like about my partner to be? And what do I plan to do about it? I think the answer oughta be, roughly: put up with it!! In other words, realize that you guys really are not going to change one another fundamentally. You will grow, certainly, and mature, etc. – but who you is is who you gonna turn out to be, pretty much.
As for some magic age, well, once you are in your early 20s, all bets are off and you might as well get on with it!! In the meantime it is nice to be free enough to travel the world, etc., which is much more challenging with infants & toddlers in tow, see!
Enjoy!