Just remember this.....once you have kids, it all changes!
My first one arrived a few hours before my 25th birthday on 2000 (Lauren was born June 17th, my birthday is June 18th, it also happened to be fathers day!) followed by Max in Dec 04 and Bubba (his legal name is Simon) at the end of January 2007........
.......the changes in the relationship after the first baby were significant but subtle. With the addition of #2 and #3 the whole dynamic changes. It is no longer about the two of you, it is about ALL OF YOU.
I've been with Susie for 10 years come this November (she swears I'm a one night stand who just wouldn't go away) and through the ups and downs we just adapt. Adapting is hard, but if you are committed you deal with it and move forward (FYI: Once you have three kids you'll want to be committed to a nice padded room).
Just remember this, if you have kids.....they come first! My job has had me on the road since I was 16. When we were just 'us' and I was gone it was hard, but OK. When we had just one child it was hard, but manageable. When #2 showed up I spent my first year on the road 3+ days a week, every week, month in and month out for a year. I ended up quitting my job as a Director of Photography overseeing 5 international business magazines (worked out well as my job was about to be made 'redundant'). I quite because I wanted to be with my son and he barely knew me, and my wife was really getting stretched to thing.
Now with #3 I have tried to create a travel schedule that lets me do what I need to do while accounting for what my wife needs as well. She has her schedule, I have my kids schedules I need to keep in mind and when I can I work around them, which can mean bounding through three continents in 3.5 days to make sure I am home for dinner on Sunday night with my kids:0)
So forget the challenges of marriage if you plan on having kids and check out the complexity of making your relationship work when there is a much more complex dynamic to your relationship.