luvdisney14 and zulaya: It must be because we're going the first week of May. Just for yuks, I tried all of the same codes for our weeklong trip at the end of October, and the price for the minivan was way over $200. I don't know what the cut-off is for the great rates, but I guess all you can do is keep trying as your trip gets closer. I was thrilled when we got $166 -- I can't believe it's gone down three times since, but I guess it's all icing on the cake.
FWIW, I do keep making new reservations when I find the better rate, then go and cancel the old one.