It is not a myth. It really does exist for many. I'm here to tell you that even sex after seventy and beyond does. While you, if you are a young reader, might consider 60+ old, I certainly don't. Isn't old age always at least ten years away from whatever age you are now?
Whatever your situation regarding desirable and desiring available partners (which will affect what kind of sex you have at any age), sex after the first flush of youth is going to be different. Senior sex will be different because both our minds and our bodies are not what they were in youth or vigorous midlife.
Mentally, we are clearer on what the minimal requirements are for good sex and an acceptable partner. By the age of 60 and beyond we ought to know what we want and how to go about securing it. One would expect that would make sex better than it was at earlier times of our life. But on the other hand, at the very least we are not as commercially desirable as we once might have been. All media define sexually alluring as young, smooth skinned, white toothed, lithe and wrinkle free. No matter how good we look "for our age", hardly anyone looks "young" after 60. So both women and men are likely to have some body issues. That is, will not feel as ready to take clothes off in the pursuit of pleasure. If you're lucky, the eyesight of your partner(s) might also become a bit fuzzier at the same time as your ears and chin do.
Physically, those over 60 will have undergone changes which affect sexual activity - for good or for ill. Neither sex is as likely to be limber as we once were. Certain sexual positions will not be comfortable or even possible. If they happen to be our favorites of long ago, so much the worse. Then again, necessity might provide the opportunity to discover some new favorites.
Post menopausal women needn't worry about unplanned pregnancy. That's a plus. But many of us need to add commercial lubrication to any sexual interactions and both have to deal with decreased desire levels. Also, the reality is that older women in this society usually have a harder time finding acceptable sexual partners.
For men erections will not be as pop-up ready as they were in youth and, for many, that's a good thing. Sexual interactions can go at a more leisurely pace, providing more sensual pleasure for both parties. Men who were quick on the trigger in youth will either have learned some ejaculatory control or Mother Nature may have provided some. Sex can not only last longer but need not be as goal oriented or ejaculation-centered, again a plus for both sexes . While by no means a magic bullet, how lucky we are that Viagra, Cialis and Levitra are now available to ageing men when they were not at previous times.
So there are plusses and minuses for sex at an older age. Those who find the emphasis on the positive changes to be found in sex as we age are likely to be the type who habitually look at the glass as half full. Those who dwell on the negative effects of age on sex will have a lifelong half-empty glass outlook.
One's whole life, not only limiting this to one's sex life, is likely to be enhanced if one is determined to see the necessary changes of age as merely differences not necessarily deficiencies. One of the key measurements of good health is to be able to take changes in stride and adapt to and with them. If one can not do that, or just gives up on sex because it isn't what it once was, it is only then that one is truly old.