yeah, all those things..condition of the wall, hormones, size...
I keep trying to find a way to 'squeeze in', er uh, pardon the language, another observation on Bill's idea the kid wants to stay and is no dummy: He knows this is the last free meal he will ever have.
If this keeps going on, you won't just give the kid that Paper Cutter; he'll be so large he'll take it from your hand and be the one swinging it overhead demanding more milk.
munk