I don't know. I'm in my (very) late 60's and still call adults by sir or mam unless asked to do otherwise, even if they're in their 20's. (Partly because I'm terrible with names.I am so old I can call teenagers young man/lady and not bat an eyelash.
I don't know if that's good or bad...
On the flip side I can now call adults by their first names, a concept that is still utterly foreign to me.
