I've got a 7-hour layover next Tuesday in Amsterdam. Two summers ago I went to Utrecht. Bert's Bierhuis had a shelf full of all three Westvleterens, and a few blocks away there was a beer fest where they were actively trying to talk passersby into spending a few of their tokens to try it.
Last summer, I went back and they (along with the local Belgian-beer pub) were lamenting that the Westvleteren disappears as soon as they can manage to get any, because there had been an article or something telling people to Utrecht to get some (I kick myself).
With a 7 hour layover, is there any other good shot at picking up a few bottles of the Westvleteren 12 in Holland (or even day-trainable Belgium) that would be worth a shot (I just got a post from someone on the whisky group who lives near the German border on the Rhein, and he says that Westvleteren is available there aplenty--but that is a long way to go without a specific target!).