You can enter as many times as you want, and that doesn't make the drawing worth it to me. I could probably find $200 in vinyl from Bayside, TBS, etc... I just know there's some Victory fanboy out there that will enter a thousand times and could find more use in his store credit.
They don't really make it clear that you should probably (I'm assuming) be logged into some kind of SoundCloud account for your listens to count ... how else would they track this?