I have had Xtol stay good in a partially filled distilled water jug for 3 months. I have also run into the mysterious 'Xtol Failure' problem of developing just fine and then the next roll, from the same batch, within a day, producing the thinnest negatives possible. NO change in anything. Same distilled water for mixing, same procedures, same everything except time. I have also had brand new Xtol produce these same extremely thin negatives right out of the package. No discoloration of chemistry, either dry or wet. No caked powder. No warning. Just failure.(posted 8650 days ago)Kodak has now discontinued recommending Xtol at dilutions greater than 1:1. No more times published for 1:2, 1:3 or greater. Partly due to Xtol performing poorly AT TIMES in higher dilutions with crappy water such as we have here in Utah. Distilled is supposed to take care of any problems, but when you get the dreaded 'Xtol Failure', you have to wonder.
Couple that with EK having problems with the 5 litre packaging, where nice little piles of white powder from Part A end up on the sales & display counters of the camera stores even before you buy it, and The Yellow Peril looks pretty stupid. Xtol can be one of the finest developers made. But with quality control like this, Kodak could be taking notes from the Soviet Army.
So, how long the solution will remain 'good' is anyones guess at this time.