why waste one's time relating something to gender, when the concept in question could be described clearly and succinctly in one word without resorting to evocative and inaccurate gender-based tomfoolery?

Well, besides gender, the -boy and -girl suffixes carry a strong connotation of childishness (or, if you're feeling generous, "a youthful spirit"), which, I think, is missing in the simple term "fan."

Yes, I know "Fan" originally comes from "fanatic," which already implies a lack of maturity and sense of proportion. But as you point out, original meanings and origins of words often fall by the wayside, as years go by. Today, "fan" is often used to mean "aficionado," so fanboy/fangirl has cropped up to fill the void left behind.

I'm all for gender neutral words, however, as long as they don't get so cumbersome they turn into tongue-twisters.

What do you say we try "Fankids" or "Fanbrats" on for size?