I assume the question refers to people not involved in committed relationships (i.e. married).
I don't see that age should have any effect on dating. A mature person (not that age is a guarantee of maturity) can bring a lot of wisdom and insight into a relationship.
Do people stop loving after a certain age? Obviously not. Love is more than sex and physical arousal or performance (and now they have pills for that anyway, I get tons of e-mails about them!). Dating is about relationships, not just "getting lucky".
However, the goals of dating probably change with age. There are many reasons to date, companionship, to share an experience with someone, to have an adventure with another person (romantic or otherwise). I don't think age would curtail any of that. Circumstances and health might affect it, but considering that dating is really about relationships, I think we humans can relate to each other throughout our lives, as long as we have awareness and cognitive ability. So obviously, we can experience love, even romance, throughout our lives.
My opinion anyway.