In answer to the question, every couple’s situation is different in what attracts them to each other. But a rather large age gap does spotlight whether there should be an optimum difference for a romantic relationship to last because simply communicating with each other could be uncomfortable.
On the face of it, there is no ‘optimum age difference’ in relationships, except if you are like the notorious Baptist minister, Glynn Wolfe, who married 29 times mainly to women who were between 17 and 21 years old, even when he was 71 years old himself! Such an age gap is almost obscene and does not take account of the vast difference in adult evolution between the parties. His wives would have been just starting out on their life journeys, while he was nearing the end of his! They would have very little in common all round.
However, apart from such extreme cases, there is usually a ‘relevant age gap’ which matches the desires of both parties. This tends t be less than one generation (18 years) in difference. More than that, and you get problems of communication, perception, and expectations between the couple. It is difficult to share experiences and memories as they would not be mutual.
For example, the older person would have enjoyed their youth already, been there and done that, so they are likely not to be interested in the kind of activities (like partying and entertaining, etc.) in which a younger person might wish to indulge. They would also be more mature and experienced, while the much younger person would need time to get that experience and maturity, too.
Again, we all go through set stages of evolution as we age (seven in all) that mould our perspectives and affect how we see the world). An older person might wish to settle down because he/she is in Stage Five or Six of their adult development (the period of Responsibility and Choice) whereas the younger one is in Stage Three or Four (the Age of Self-Discovery and Experiment). It means one person will perhaps be keen to settle down, to make life choices and begin the process of taking responsibility for him/herself in a mature way, while the other person will be busy discovering their world and finding out about themselves first. Two different ways of seeing life, especially if they find it hard to compromise. In time, those two opposing perspectives are likely to create a lot of impatience and misunderstanding between the couple, which then makes a longer term partnership less likely.
That is the main reason why relationships with huge age gaps can be problematic. If the people involved do not grow together, or come to share the same perspectives, it cannot survive. Personal tastes, particularly in music, fashion and knowledge, which determine perception, would also be very different because a huge age gap is almost like a generation when it comes to our lifestyles. That would lessen the things the couple can relate to between them, which eventually means having different sets of friends to connect with who can validate and affirm each party.
In the end, it really is what’s comfortable for both parties. There isn’t any optimum gap in reality, as long as one bears in mind that a wider age gap makes it less likely that the relationship will last, because it will have very little foundation, in mutual experience, aspiration and shared perception, to sustain it.
Source: Richard Barrett: 7 Stages of Psychological Development