I hate how everybody always brings up the "paralyzed from the waist down" and "when we're 90 and wrinkly" scenarios to justify a lack of sex. I had to look it up and 29% of men and 25% of women are still sexually active after age 80. If you consider the high percentage that would no longer be mated at all or physically separated due to health issues, the percentage of couples living together still having sex would be quite a bit higher. I wouldn't want to have sex with a 90 year old guy right now but, hey, I wouldn't have wanted to have sex with guys in their 50s when I was in my teens either but I've managed to adjust.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver