no. i do not *actually* believe that washing my belt will wash away my knowledge. that's silly. but i do like the metaphor. so i only wash it if it stinks (almost never) or gets something particularly gross on it (blood, dirt or mud, or something spills on it). and yes, i agree that folks are way too wound up about this topic. ringworm and staph have been around for ages, and i strongly believe that the reason we have so much trouble with it in the US these days (as opposed to countries where hygeine is not as vigilant) is because of our over-reliance on antimicrobials and antibiotics. we've weakened our immune systems to the bugs and germs that are all around us all the time (and we've also bred "super bugs"). a lot of folks are gonna scream and cry bloody murder about this. *shrug* let 'em. they may call me dirty. and i may call them prissy. whatever.
i wash my gi after every single wear because if i don't it stinks. a belt doesn't collect skin the way a gi does, and it gets only a fraction of the amount of sweat. hanging it out after every wear is sufficient to prevent any significant odor. it's not like there's a dormant odor that reactivates with sweat like a gi does, because it doesn't collect funk the way a gi does. i've trained in judo and TMA schools where this practice was the norm. i've never had a skin infection, have only known one training partner who's gotten one, and the only time odor has put me off was with a dirty gi or a dirty person in the gi. and yes, i've got a very sensitive schnozz.
as long as you're airing your belt out and not letting it sit damp in a bag, it's not going to ferment.
ppl get ring worm and staph infections because it's a part of socializing and personal contact. if you think it's "entirely preventable" you're fooling yourself. everybody will deal with this shit in some form or another at some point in time. maybe it'll be via bjj, maybe it'll be from the stray cat you pet on your way home. or maybe you'll just be in the wrong place at the wrong time. who knows.
i'm not gonna argue about it. just sayin my peace.
cheers!