Being Called "Kiddo"

There's an older gentleman I know who always calls me "kiddo" when he sees me. "How ya doin', kiddo?" I think it's kind of funny. If it was anyone else, this might bother me. But it made me wonder, how old would I have to be for him to stop calling me that? Is it a compliment (he thinks I'm younger than I really am) or something he says to everybody (under age 60)? Now that I have a "kiddo" of my own, this is particularly funny.

Speaking of my kiddo, here's a recent photo. (This is right after his very traumatic first haircut!)