IME it seems like lately the best stuff doesnt really move until they are just about to drop all of the new season stuff and then you start getting those drops or codes or both as Yoox finally "blinks" and decides to move the stuff on to make room. They know they have a built in buyer for the item at a certain price because of the dreambox data, so they wait and hope someone comes along and picks it up at the higher price (which occasionally happens) and they can pick up some extra incremental revenue. If noone comes along and their getting new stuff and need to move it on, they drop the price and throw it to us dogs to fight over.
I suspect that both Yoox and the users have gotten savvier over the years and the result is that it's much tighter to find really good deals. This is true for at least for the obviously nice stuff; there's still the odd fancy cashmere sweater or Caruso made suit that occasionally gets discovered under some goofy name (looking at you "SHIRTS & TIES").