The Image Permanence Institute makes available the IPI Guide to Preservation of Digitally-Printed Photographs. This guide is intended for libraries, museums, and archives, but it is also useful to others.
Here are some highlights:
- For digital prints the primary drivers of deterioration are heat, moisture, and air pollutants.
- High humidity should be avoided for all photograph types to prevent blocking, ferrotyping, and mold growth.
- …inkjet dyes can also bleed severely when exposed to high humidity causing noticeable image blurring and color fringing.
- A variety of gases in the air can cause damage to digitally-printed photographs. Oxidizing agents such as ozone can cause fade or yellowing of many print types as well as embrittlement of inkjet paper coatings. Nitrogen dioxide can induce yellowing in all print types and bleed in some dye inkjet prints.
- Enclosures of low permeability, such as polyester sleeves, are helpful in reducing the rate of pollutant damage.
- …no PSA [pressure sensitive adhesive] should be applied directly to an inkjet photograph even if it meets ISO 18902 or passes the Photographic Activity Test (PAT).
- The major concern for prints on display are fade of the colorants, yellowing of the papers, and/or embrittlement of surface coatings.
I have seen yellowing and fading of inkjet prints that I have displayed, especially with prints produced on matte inkjet paper. Have you seen similar problems?
All About Images Blog 
“I have seen yellowing and fading of inkjet prints that I have displayed, especially with prints produced on matte inkjet paper. Have you seen similar problems?’
Yes. I have seen this with papers that use optical brighteners, such as Epson Matte Paper Heavyweight (which I think is now called Premium Presentation Paper Matte).
Papers without optical brighteners, properly stored and displayed, should not have this problem. I now typically use Ilford Smooth Pearl and Gold Fibre Silk and I no longer experience this problem.
Mark, I expect the fading, etc. you are seeing has more to do with the ink than the matt paper. I seem to remember that you print with a printer that uses dye based inks rather than pigment.
In this particular case, the problem is the paper. Older prints displayed in the same location and printed on the same printer with glossy paper show no sign of fading. The matte paper that I used is more vulnerable to air pollution and other problems than the glossy paper.
Mark, I’m curious as to the specific paper and printer used. Also, how old are the prints?