Wilhelm Research, which tests various print media both photographic and digital to see how long they last before they start to change color and/or fade away, has published its test results for black-and-white prints made with the Canon Pixma Pro 9500 and Canon Lucia pigment inks. The clear winner was Canon Photo Paper Plus Semi-Gloss, which under acellerated light and humidity testing is expected to last at least 300 years.
When printed using standard Canon inkjet inks, the same paper tested to last 104 years. In both cases, the results were based on photos displayed framed under glass. When stored in darkness their longevity goes up. When left out in the open, they fade sooner.
It's a worthwhile read if you are interested in making your own inkjet prints.
Download the PDF file.