Really dumb question about marriage and sex

[chaosphaere]

Do people who have been together for a very long time - say, thirty years or more, even fifty years - still have sex? Much has been made out of the fact that after a long marriage, people are mostly in a friendship... but are they still even sexually attracted to each other at all? Will they tend to look back and remember the young romantic days with nostalgia, and have moments of "zing" with their partner on occasion?

Finally, is there any literature out there that shows an aged couple who still have a happy sex life?

Sign me, the one person who isn't put off by the thought of old people having sex.