"Until last year, when Miami won, the average age of an NBA championship team was 34 and up, and so that goes to tell you that you have to have that veteran experience, that leadership that knowing guys have been there before. And so, that's why I like our team. You got that with a good mix of young guys and you got yourself a championship contender."
Not exactly sure where Terry got that stat (nor do I think it's accurate), but it really doesn't matter. The Celtics don't think they're too old to bring home Banner 18 and that's what matters.