Stop baths are more often "rated" by the number of prints (or rolls of film that they will effectively stop development of. Indicator stop of course changes color when its potency is used up. Shelf life doesn't really apply to stop baths. Another way to test is to feel the print after its been through the stop bath - the general slipperyness of the developer should be gone.(posted 8390 days ago)To answer your question about general capacities of a stop bath, go to Ilfords tutorials on processing RC and fiber based prints, some capacity infornmation for their various chemistries is listed there.