Whenever I am in doubt whether to change my socks or not I follow this simple procedure.
I bring them near my sister's nose. If she screams "AAAAAAAAH! BADTAMEEZ(mannerless)!" and gives me a tight slap, then I infer that its the time to change socks, which I do.
If she doesn't slap me, well, so far it hasn't happened that I wasn't slapped by her.
My girlfriend changes my socks!
Oh yeah, who is she?
MIND YOUR OWN BUSINESS!