Storage and Care of KODAK Photographic Materials Before and After Processing
...Making and using an expendable duplicate transparency for projection or display will spare the original image. Make duplicates of original slides and transparencies by direct printing on KODAK PROFESSIONAL EKTACHROME Duplicating Film EDUPE.
...Prolonged exposure to light and heat adversely affects most photographic dyes. Do not subject valuable original slides to prolonged or repeated projection, e.g., in a commercial display.