When I was a psychology student at the University of Washington http://www.washington.edu/, I took a class called "Psych 210." This was a class on human sexuality, and I recall being quite interested in showing up every week. The instructor's frank manner was fascinating to me, as she stood in Kane lecture hall in front of over a hundred students, teaching us the facts of life with a detail that my parents, who had sat me down for the birds and bees talk at age 18 (better late than never?), could only have dreamed about.
I remember many things from that class, but what I remember most vividly were two videos that were shown of (straight) married couples having sex. The first was of a young couple, and I remember how they looked--like models in magazines: tanned, toned, and athletic. Not unlike the narrow body-type standard evident in much of mainstream pornography today. They had sex in many different positions, and they seemed to be having a good, lusty time of it.
The second video was of a couple in their elder years; perhaps mid-70's. They too were filmed being sexual, and my experience of watching was quite different. I noticed their bodies, as I had before, and saw that they were shaped differently--wrinkles, folds of skin--signs of aging, of course. But after my initial surprise, their appearance had almost no meaning compared to what really stood out to me in their sexual exchange. At the time I didn't try to describe the difference between the couples. I was about 19 years old; I just watched. But now I can say that what I saw, and what seemed missing from the vigor of the first couple, was emotional: affection, laughter, patience, and joy. At one point, the man's erection went down. His wife didn't protest, she simply giggled playfully and and stimulated him more directly. Later when they moved toward intercourse he discovered she was vaginally dry; the husband made sure the lubrication was warm before gently applying it. They went slowly. They smiled.
A simple way to say what I saw was that the first couple seemed to be having sex, and the second couple was making love. While the first couple seemed to have sexual stamina, the second had sexual and relational endurance.
This link to a short Psychology Today article talks about what elder couples (with happy sex lives) can teach younger ones. In order to have a new sexual r.evolution (empowered by the Internet), we're going to need all the wisdom we can get!