According to some psychologists who have studied the matter, the single most powerful predictor of whether a couple will divorce or not is this: Whether they express contempt for each other. In the psychologist's studies: Couples that expressed contempt for each other inevitably divorced. The "contempt factor" outweighed all the other factors combined in predicting who would divorce or not.
After reflecting on their studies, I've come to believe that much marital advice is misguided. For instance, we tend to think that couples who argue a lot are unhappy couples and therefore likely to divorce. But the psychologists found that argumentative couples did as well as anyone else -- provided they were not contemptuous of each other. So, I'm willing to speculate that an age difference is less of an indicator of who will divorce and who will stay together than is mutual respect.
After reflecting on their studies, I've come to believe that much marital advice is misguided. For instance, we tend to think that couples who argue a lot are unhappy couples and therefore likely to divorce. But the psychologists found that argumentative couples did as well as anyone else -- provided they were not contemptuous of each other. So, I'm willing to speculate that an age difference is less of an indicator of who will divorce and who will stay together than is mutual respect.