Light-fastness
From The Glossary of Digital Photography
The length of time a print will last under a particular lighting source. All photographic images fade over time. Some may last only a few months while others may last two hundred years Factors that determine light-fastness include the type of light, how the print is displayed (e.g., under glass, and if so, the type of glass), the paper or media the image is printed on, the technique used to print the image, and other materials used in the image's production or that touch the print.
