The pigment ink prints from the latest Epson and Canon printers (Ultrachrome K3, and Lucia ink-sets) that I work with are very light stable, waterfast, and can endure high temperature. But they do have one weakness that the photography conservation community has identified. The receiving layer (the layer on the surface of the paper that holds and binds the ink) remains absorbant after printing and will absorb pollutants exposed to the prints.
Upon a recent visit to one of my clients I noticed that prints were being stored in non-archival cardboard. The cardboard had gotten damp and it caused some yellowing on the edge of the print. the print was acting like a blotter and sucking the extra moister out of the cardboard. To avoid this I now deliver all prints in Polyethylene (PE) bags. Please, if you are storing prints place them in archival bags, or better yet put them in a nice frame behind glass so we can all enjoy them!
Also, when ordering prints in the future, if you plan to store the prints for long term, please ask me for archival packing in addition to the Polyethylene bags. There is an extra charge, but it’s a minor charge to protect these prints that will last for hundreds of years.