From tests results of 1998 Wilhelm Imaging Research,

Years of Print Display before Noticeable Fading Occurs--

Fujicolor Crystal Archive Paper ... 60 years

Kodak Ektacolor Edge 7 and Royal VII Papers ... 18 years
Kodak Ektacolor Portra III Professional Paper ... 14

Konica Color QA Paper Type A7 ... 14 years
Agfacolor Paper Type 10 ... 13 years

See their writings and web page for all the details.