I used 3 pieces at first, but for reasons already mentioned I now use only 1-piece airlocks. Even when there are no visible bubbles in your wine, with a 1-piece you can tell if anything is still going on fairly easily. Just look at where the bubble is, and several minutes later look again. Also, most times when a fermentation really is complete, the 1-piece will "balance out" the water level on both sides which is a very obvious way to easily tell that fermentation has stopped. There is no method to tell this with a 3-piece. I have not had a 1-piece dry out to the point of air getting in, and I have actually let some sit unwatched for over a year, so that says a lot I think. Since I only do 1-gallon batches, I see no need for a 3-piece, even a ridiculously active primary fermentation does not put out too much gas for the 1-piece to handle.