I'm on my first bottle of Rodinal and I've noticed that it's started to become discoloured already. What sort of shelf life should I expect from this once started? How can I tell when it's become degraded to the point that I should discard it? What can I do to improve it's life? I suspect that flooding the top of the bottle with nitrogen or expelling all the air would help, would refrigeration help?

Having read the leaflet I couldn't find any guidance on these issues.