There are a lot of things that need to be considered for this question. Are both people completely ready to settle down? Have they, "sowed their wild oats?" I'm not saying that this expression applies to everyone but this is why I say this.
I met my husband at seventeen. For a long time, we were so deeply in love, but in reality neither of us so called, "experienced life." It doesn't mean that love wasn't there. We separated for a time. During this time it gave us both space not just know other people but to live and experience life. I married him at the age of twenty four. Nine years later, we still have small marriage quarries at times, that make neither of us happy. We learn how to work through them and move on. I think we both thrive in our relationship together.
Also one should consider that a marriage is a full commitment. Trust, devotion, and communication are key aspects. To break it down I don't believe age applies here. I'm sure others might disagree. I think it depends upon each couple differently and the commitment that they are willing to devote to one another.