I use the JOBO C41 press kit from B&H. I develop 30 4x5 sheets maximum (as per specifications) in 3 batches of 10 in a Jobo 3010 drum. I never use the chemistry more than the recommended max quantity of film. I've tested my process with control strips before the first negatives, during the middle batch, and after the last batch of film was processed. There is a detectible drop in densitometric measures (i.e., densities moving closer to control limits), but still under control by the end. My negs are too important (really too expensive) for me to experiment with stretching it any further
Hope this helps.