my sister has 4 kids, 3 boys (11,9,7) and 1 girl (5) - and the boys are all gross - granted they are bit younger than your DS, but they all have to be told 1000 times to shower, clean nails, teeth etc! her DD is at the opposite end of the scale and cant stand any dirt - so maybe its a boy thing! As for growing out of it, i dunno, my DH is 34 and can still be a feral !