I am using my 1 litre still that I got on the Ilford trip in June 2006 and started using about Sept of that year. No special storage. Just a squirt of protectan each time I replenish the Nova slot. My printing has been very low volume
Once opened my guess is that you will use each 1 litre long before it goes bad. If you intend to stock several containers unopened then much longer would be my guess but you need a more accurate answer that I cannot give. I have been impressed by its longevity in very low volume use.