I understand about the tanks. But Kodak is usually pretty good about supplying instructions for both commercial labs and hobbyists using small tanks. So it's frustrating that I can't find Kodak's recommended shelf life for working strength fixer in full, sealed containers.
I am not really concerned with fixer capacity. If I were to shoot 4 rolls of B&W 35mm film in a month, that would be extraordinary for me. I do mark each roll on the jug of the working fixer as I reuse it, but time is going catch me long before I exhaust the capacity.
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Thanks again to all the forum members for sharing your wisdom.
It would be difficult to say how long it will last. Adox says it's concentrate should be used within three months, once opened. For me it lasted two to three years, except once. Working solution up to a year. For you it might be the same or it goes belly up (actually sulfur down) after a short time. Depends on you and your environmental conditions.