Quote Originally Posted by Ian Grant View Post
It depends on the packaging used, some older plastics used breathe oxygen very slowly over time and chemistry oxidises, this happens with some liquids as well where high quality high density polythenes etc aren't used.
As Ian says it all depends on the packaging. I believe that Kodak's is the best in this respect. I wish they still used metal cans. I have some film developer that is government surplus from WWII which looks like it was made yesterday! It is sealed under nitrogen.