We have experienced something called 'mordantic' fading, even laminated - after a week prints would fade terribly. The media was wholey responsible, the coating was incompatible with the dye based (Encad GX) inkset we were using.
Have you read this forum topic:
Business support forums - Fading issue with dye based ink in Designjet 5500
The pertinent section is:
We've found two things that may be causing this:
1) The HP instant dry gloss paper. We no longer stock this paper, since it was the worst culprit (and had other problems, like sticking to itself and ruining prints)
2) Exposure to ozone. Some customers have ionizing air filters in their homes and offices, which generate ozone. The prints exposed to these devices faded rapidly (within weeks). The fading was less on satin papers, but still present.
Our solutions:
1) Educate our customers - discourage any display of prints without lamination, framing behind glass, or a protective spray like Print Guard or Bulldog.
2) Elimination of instant dry papers from our stock.
This has solved the issue for us since the dye products aren't likely to be changed anytime soon. We chose not to switch to the UV ink set because the color range and accuracy of the dye set is substantially better.
http://www.imagesetting.com