I use ABC pyro in 5x7" tanks (4 and 5 quarts) when I have a lot of processing to do. I find I can consistently put three batches of hangers through the developer, as long as I have them lined up and ready to go and mix the pyro in just before the first batch. By way of comparison Michael Smith says he runs two batches through ABC pyro in trays, but in a tank there is more volume of solution per sheet and less surface exposed to air relative to the amount of developer and probably less churning when lifting the hangers every 15 seconds, as opposed to shuffling a stack in a tray.