My husband and I met in high school and we've been together ever since. I was two years behind him and wanted to go to college before we got married so we were together almost 8 years before we finally got married. We'll be married 8 years come this November.
To answer your question: I don't think it matters when you meet your spouse, what matters is the amount of work the two people are willing to put into the marriage/relationship. And obviously the two people have to be right for each other and sometimes it takes a specific situation to find out that two people aren't right for each other.
Some things I've learned from being with someone for over 15 years is you have to work at your relationship every day, you can't take one another for granted, and you must always communicate with that person.