I married a man several years younger, and here's my take: If you were born in the fifties and came of age in the 60's, you have lived through an experience that no one who didn't can ever understand. You may have developed musical tastes that are quite different from the stuff that came later. The politics of that era left scars on all of us, especially the Vietnam war. I find that that missing 5 or so years creates a gap that can't be crossed, and inside jokes that can't be shared. I've come to the conclusion that I should never be with anyone who doesn't know that Abby Hoffman wasn't a chick. Besides, I really prefer older men who are a bit chastened by life, who don't have the young man's arrogance.
   That said, if you are decades younger than I, and your mate is several years younger, I don't know that it makes as much difference.