I don't personally think there's an definitive age to get married, because maturity is different for everyone. Some people never get mature enough to marry and be stable, even past 30.
To me maturity, marriage wise, means that you're *commited* and serious about making it work. You get past the issues and actually deal with them... Anyway, if there's an issue, you should be able to tell him/her, because marriage is founded on love and trust.
Age has nothing to do with it.