Only just got round to trying this. Not needed it yet (still don't).
It seems that almost all the AP's around here have some kind of rate limiting thing where if you hammer it with pins then it locks you out after a few tries, for five minutes at a time. However, couple of days in and I'm at over 20% done...this is a vast improvement over the four years it would have taken me to bruteforce a WPA key on my main machine that was ten characters long, and all uppercase alpha-numeric (which is what SKY broadband wireless passwords are according to forums).