Thank you all for your comments.
I've read a few good arguments against issuing a warranty in this thread and I can see your point, but I will go ahead with it.
The main reasons for me to do it is:
1) Provide the buyer with a do/don't recommendation list and
2) (as Mr. Lambrecht clearly stated) "replace what is obviously bad craftsmanship on my part".
By this I mean that I'm pretty sure I am doing the best I can regarding archival longevity, but if not I need to know in order to improve my process and have my photographs live as long as possible.