Personally, I know 0 people who have been married longer than 5 years that are still happy. Some are content, most aren't. I don't like those odds.
ymmv
Edit: And now that I'm 35, the wave of divorces has begun. 3 of my married friends are going through divorces just this year. All initiated by their wives... who pressed them to get married in the first place.
Edit again: My mistake. I know one guy who's happy but dude married a Disney millionaire so his situation is a bit of an outlier.