most people I have encountered in this game where age had come up in conversation, seem to be around 17-30 age group. The oldest person I have come accross is myself at 42 at this point. Although, as you say, there are much older folks playing for sure.
When I played another MMO (WoW), we had a player in her 70's who was a raid healer and a very good one at that. the rest of the guild was mainly made up of mid 30's to mid 40's with a splash of 50's in for good measure. We also had younger peeps also but just a few.
I guess old farts sort of accumilate over time