Aragorn is an extremely special instance in that, in a way, this feature belongs to the entirety of Elendor and not just the Arnorian culture. However, in the last few years (and most recent incarnations) of the character, it has become common practice for it to be awarded to a member of this culture, as we tend to believe it should be! ;)

     The honor of playing Aragorn carries with it a great responsibility to role-play and play well, not simply for Arnor but for Elendor. As such it is a very exclusive position and not the sort to change hands very much. For IC knowledge of Aragorn, well... read the books!