I have a collection of my grandfathers slides and negatives going back to the 1920's. Of course the color E6 and C-41 date from the 1950's. The early E6 Stocks from the 1950's can be quite deteriorated. The Kodak stock seems best but all the Agfa and other stocks show major color loss and shifting. By the 1970's all the E6 stocks seem to hold up reasonably well. With the exception of the "commercial" slides, (something you would buy at a gift shop on vacation). These commercial slides have all faded and lost nearly all the colors except some faint reds. I have several sets of commercial slides spanning 4 decades and all have suffered this fate. The C-41 color negatives seem to have come out fine. I have less older ones and mostly all Kodak. The films that have fared the worst are the B&W safety film stocks from the 1940's some of these rolls have had the silver slide off the film and pool at the bottom of the can... Others have crazed and crystalized...