Hi there TheBongolian
I guess I should have answered this post long ago. Apologies.
It's a complicated subject and depends on the ink, paper, storage conditions, etc. etc. The de-facto expert is generally considered to be Wilhelm Research (see http://www.wilhelm-research.com/
). There is a lot of info on their website, but it normally only serves to further confuse. Should you have specific questions he does often provide answers on the printing forum of Luminous Landscape (see http://forum.luminous-landscape.com/index.php?board=6.0
regards - Peter