It really depends completely on the individuals involved. I've seen marriages between relatively young people work, and marriages between "mature" (chronologically only) people fail.

Being in the military, you meet people from all areas of the US, who come from all types of backgrounds. In some areas a 16 y/o getting married wouldn't be unusual at all. (This created some interesting issues for the Army when someone from a state where the legal age for marriage was 16 moved with their spouse to a state where the legal age was 18. In some instances the Army had a hell of a time fighting legal issues involving statutory rape, transport of a minor across state lines, etc.)