Age has nothing at all to do with "geezerness". It's a state of mind. I've known people in their late 20s who were very clearly geezers, and people in their 70s who were very clearly not.
If you want to look to the mass media for your entertainment, that's fine. Just don't tell me that's the standard for anything: age, looks, musicianship, ... What "makes it" on radio and TV is simply whatever's best for keeping the audience's attention between commercials. That's the only reason it's there. It's not art. It's not culture. It's advertising. Don't forget that.
Is B.B. King a geezer? How about Eric Clapton? Jimmy Page? Eddie Van Halen? Hmmm... What is it? Do they sound like geezers? Look like geezers? Act like geezers? How about Carlos Santana? Johnny A? Bruce Springsteen? Neil Young?
For that matter, what about Les Paul - where would modern rock be without his contributions, both technologically and musically? He's in his 80s, and still doing his thing. Is he a geezer?
Or Peter Green - he's not only getting on in years, he's also feeble (as in needing a stage hand to help him change guitars)... Is he a geezer? If you saw him play, you'd have your answer.
Ever see Papa John Creach play with the Jefferson Airplane (when both were alive)? He was ancient, but had more sparkle and fire than any three of the other players on stage.
I don't care how old the players are. If they're good musicians, and they play something I enjoy hearing, that's all it takes. Even if they're young... or old. Whether or not they share my fashion sense, cultural references, or political views. Music has way too many genre and gender distinctions already. We sure as heck don't need to start subdividing genres according to age.