Are we talking about language learning? I have some preference for adults but beyond that I don't care much. It seems like a large majority of people here are young adults though so maybe you don't have a choice ^^
I am not bothered about people's age when we are talking about languages exchanges, but I must admit that the best language partners I have had were quite older than me. They tend to be more serious, patient, focused on learning the language and willing to help.