I'll admit, I'd love to get rid of extra stuff too, but I never stock my vendor until I know its okay. If I can't be around the morning of the festival, I'll stock it the night before as late as possible. The stocking rule has been in place in every festival I've attended, although quite a few ignore it.
What bugs me more than the stocking early, is those that stock items that aren't rare like haven barrel hoops, etc. I wish we could come up with a set of universal rules as well as a system to ban the items like the aforementioned. Perhaps the hosts keeping track of whose vendor is whose and they are messaged to remove the item and if they don't, than they are banned from having a vendor at the next one. Can they find a way around it? Sure, but I'd like it if at least we made an effort to protect the integrity of the rares community as a whole by publicly taking a stand against it. It really hurts our reputation and imposes the sense that the entire community is about greed more than education, safety and passion.