Vierville

I've had a few sets of Aeromaster 1:48 P-51 decals in my stash for at least a decade and I've noticed that some sets are printed more sharply than others and alarmingly also that some sets seem to be suffering from slight yellowing of the decal carrier film. They've all been stored together in the exact same conditions and so I was really puzzled. I examined the sheets carefully and then I noticed...the ones that were affected are all 'printed in mexico'. All the rest which are not affected are 'printed in italy'. Has anybody used the Aeromaster 'printed in mecico' decal sheets after years of storage and if so how did they behave on the model? Any problems? Thanks in advance!