I have received pin codes in the past, but never w/a trip already booked. The ones I get thru email are usually after pricing out trips on Disney's website & saving them. Then I get some in the mail if it's been a while since our last trip & we haven't booked anything yet. I have also received a few pin codes thru the mail for my mom b/c she went w/us back in 2008.
I use discounts every WDW trip, but this is the 1st time I have been able to apply a pin code that works for when we are going. BTW, I priced out 3 trips for Nov on the website last month & only received an email telling me to book, but no pin code for those. Then last week I priced out 2 trips for Oct & I got the pin code yesterday for Oct.