I'd say permanence should be taken very seriously by anyone selling
photographs, from limited editions at four-figure prices, to portraits
and weddings for retail customers. People treasure albums of photographs
and I think they expect the things to last. (Color--C-print--albums have
already started this trend: many folks have better pictures of their
grandparents in b&w than of their own childhoods in faded color). The
current fashion of video-taping weddings may lead to some of the legal
problems you mention, when folks find out just how limited the life
expentancy of video tape is.
I've seen firms offering "restoration" of old family photos. Retouch out
the fading, the rips and tears and coffee stains in PhotoShop: then
output a dye-sub. I don't think the customers are going to be happy to
find that the restoration has faded to a ghost in 1/4 the time the
original took to deteriorate.
By the same token, platinum devotee that I am, I like it for the look,
not because I think the longevity of platinum prints is an enormous
selling point against the longevity of properly processed silver prints.
A couple generations is probably enough to think of as "archival". A
couple decades definitely is not.
---Carl