You can't start too soon. That said, it takes as long as it takes to find a sponsor and in the meantime you can just go to meetings.
Don't worry about how old people are. Alcoholism doesn't care and neither does serenity, peace, and hope. In addition, it's advantage to learn from people with a lot of life experience. They've forgotton things you haven't even learned yet, have made mistakes you haven't made yet, plus most of the ones you have, and they have so much to teach us.
Our society is so screwed up about old people. Old people are one of our most precious resources and should be cared for, reveared, and listened to.
There's much to be learned from all people of all ages and it's valuable and important. I just submit that there's potentially more to learn from old people.
My two cents.
P.s. I'm 46, but I've also been every age before it.