There are different papers, printers and inks. And, of course, there are different conditions where the prints are stored or diplayed. All of it affect the longetivity of the print. You probably heard or read about different lifespans of a digital print, but were those statements as true as it realy is? The following article (in PDF file) casts some light on when you can expect the skin tones on your photo turn green (or yellow?).
Want to learn more? Here is the list of articles for you.