This post is what inspired me to suggest this
http://forum.c-rpg.net/index.php/topic,16105.msg230316.html#msg230316Many people will just dump the looms that get nerfed badly onto people who wanted them etc, thus screwing over the unsuspecting person who had the trades up because we get absolutely no warning of item changes before they hit
It is only fair imo, give people a chance to alter their marketplace demands to adjust to the item changes, as their wants may change