Thanks for the warm welcome guys! Hopefully my patience will pay off. I really appreciate the advice.
Patience will almost always pay off. You'll hear so many stories about how people have been chasing certain pieces for months, or years, and they're not necessarily the rarest posters either. People like Thierry and me usually have a strict budget in mind, and the one's we're after will come and go for prices higher than we're willing to pay.
But I'll tell you, the posters I got a deal on are the ones that bring me the most satisfaction. It feels more like something I earned rather than something I bought. If you're willing to wait, you'll always get what you want.
If you're like Mel and found a way to grow money out of an enchanted windowbox, you sometimes have the luxury of buying something special regardless of the pricetag, which is fine too. But chances are, if the pricetag is that high, you would really benefit from some time to think about it. There've been posters I "have to have" that cost too much and I've been on the verge of dropping too much money to get one. But after a couple of weeks, or months, of trying to find it, I realize that the appeal has diminished and no longer want it.
So, in both ways, patience pays off.