Science is starting to show that creatures who have less sex tend to live longer, but why would they want to?

Okay, that last part was my question. Really, researchers at the University of Sheffield have shown that certain beetles live longer if they avoid mating, and they believe it has something to do with hormones produced that undermine the immune system.

According to the Daily Mail:

 Despite the mechanism not being the same in humans, study author Dr Michael Siva-Jothey believes the principle can be applied.  He said: 'Nuns tend to have a longer lifespan than women with children and most people know of someone with a maiden aunt who seems to live forever.

So, is it a lack of sex that helps nuns and "old maids" to live longer?  Or is it a combination of other factors?

After reading this article, I hope that I am gone by 60 or so.

(Daily Mail)