Unfortunately there is no rec.toys.lego.marketplace, so all your posts must go to rec.toys.lego. If you post updates daily, you risk annoying people. If you post updates weekly, you probably won't annoy anyone.
A happy medium is to send updates via e-mail several times daily (whenever something relevant to a bidder changes) and to post updates to the newsgroup weekly.
8 Jan 96 [TSL]