RPC. It is a question of what constitutes "white" and as you say the effects on colour balance. If the effect was simply that white parts of the print had a slight creamy look then this might be OK but if skin tones can't be made to look right then this becomes very noticeable.
One pack as far as I can recall was purchased from new and I think PE is suggesting that 4-5 years isn't that old. The other pack was obtained via a seller but someone whom I trust when he says that it was properly stored. He estimates it may be up to 6 years old but the box has a higher CAT number than the purchase from new box. Does this means that it isn't as old?
PE As I have the boxes how easy is it to establish manufacture date and how do I go about it. I am in the U.K.?