A lot of the title of Tribe member is based off of having helped people, interacted with the community, showed game knowledge and presence, and had high participation.
While how long you've stuck with the game is truly amazing, helping/conversing with everyone takes it to the next step. You've showed your involvement.
Which is more impressive? 5 years spent on a game with about 5 days of playtime, or 1 year spent on a game with 30 days of play time? Each one is good in its own way, and it just so happens that Tribe member is rewarded for the latter.