As I understand it Kodak had a packaging problem mainly with the 1L sized packages. They are supposed to have gotten it fixed as of date code 0025.(posted 8803 days ago)If either of the packages is caked (not free flowing powder) don't use it, it will give you odd results. Kodak will replace it and may even throw in a couple extra packages.
I have not heard of people having trouble with storage of Xtol once mixed.