Thanks for a concise explanation, but one question remains...being on the lazy side I have long used C41 stabilizer (with formalin) for both E6, C41 and B&W, the latter in place of mixing separate Photo-Flo. I reason that B&W contains inherent biocide (silver), but a rinse in formalin containing stabilizer doesn't hurt. That lets me keep one liter of universal stabilizer that I generally replace about once a year, or whenever it seems to fail the sniff test--not smelling of formalin. I do re-use the bath with a few cc being lost lost in each processing.