Digital BW, The Print

>[snip] In addition, until I get some degree of certainty about about a
>lifespan of these prints, the prices I charge for these will remain
>very low. I just couldn't feel good about putting this type of print
>alongside an archivally-processed B/W silver print. [snip]

What is a good reference to what "an archivally-processed B/W silver 
print" is, what its longevity is, and how that was estimated? Is it 
in Wilhelm's book? I remember him saying something on his web page 
about Crystal Archive prints being a standard (60 Wilhelm years I 
believe) inkjet prints should strive for, but I think those are color 
prints?

Sam