http://www.luminous-landscape.com/essays/the_weakest_link.shtml
It's something of a self promotion, although the article does make clear about the author's connection to the software he is advocating. In summary, it seems that the colour inks fade at different rates, with yellow being the least permanent. You might think that this might not be a problem for mono, but often the printer driver uses the colour inks in addition to the black and greys.
It also gives some information about how ink and paper combinations are tested for light fastness. After all, digital printing only started in the last 10 years of the 20th century, so how do we know that a print can survive for decades? Answer: accelerate the fading by shining a very bright light on the print for a few days.
In the very early days, it was usual for prints to last just a matter of hours before fading back to being plain paper again. One of the reasons why Epson is so dominant as a printer manufacturer today is that it was fully involved with the technology from very early on and has invested a lot of time and money into research to improve its products.
This book http://www.amazon.co.uk/The-Art-Nash-Editions-Photography/dp/0321316304/ref=sr_1_17?ie=UTF8&qid=1349609967&sr=8-17 describes what went on in the early days. Did you know that Graham Nash, of Crosby, Stills and Nash fame, is a keen photographer and was a pioneer of printing photographs digitally? He bought an IRIS proofing printer at the end of 1989 for $126,000 (back then, the price of a house) and in association with Mac Holbert adapted it over an extended period for photographic use. Due to its historic status as being one of the very first inkjet printers used for photography, it is now in the Smithsonian, having been in use for around 15 years until 2004.
http://americanhistory.si.edu/collections/object.cfm?key=35&objkey=1107