There are no rules about this. Most of the people on this sub-forum seem to be 30+ and it goes up from there. It's whatever someone feels makes them a more mature member. These same people also post on the other sub-forums, so that's good. It can be that you know some IRL people later in life, have EC friends in later in life, or just have a feel for what later in life people are going through and want to join the conversation.