>I am just going off the spec sheets for shelf life. I am not sure what
>happens as the resist starts getting old.
As I understand it (I think from someone mentioning it here), the
film will go bad from the edges in - oxidation or something and the edges
being the unprotected bit. Potentially disastrous for a company using
it's full width in a double roll laminator in a production setting, but
mostly just an annoyance for hobbyist types. However, I sell things for a
living and I completely understand your concerns.
Russel has a good point - test it every so often. I'm not sure what to
look for though, hardening? Poor adhesion? Loss of photosensitivity? A
color change along the edges and separation of the cover sheets at the
edges would probably indicate failure in those areas, and should cast
suspicion on the areas farther toward the center. Information on this
would be useful to those of us with more than a small supply of the stuff.
-Gary