I think rule 1b has been relaxed as DS and the core SPS crew have gotten older. As you near middle age, it becomes more evident that 21 year olds may actually be more kids than adults.
Yeah, I'm pretty sure I don't consider most 21 year olds adults, regardless of what some message board's rules are. Legally, at 18 you can be considered an adult.... but you're not.
When you have your own job, pay your own bills, etc., I'll put some more thought into what I call you. Even then, you might get a "kid" from me.