I just bought a box of Acros film and it is to expire on 5/2014. That's not all that far into the future so I'm wondering what is the typical shelf life of this film. Is it usually 2 years or so? Are all films roughly made with a 2 year shelf life or do they all vary? I'm not worried about this particular box. I doubt it will last me more than 2 weeks. I'm just curious. Thanks!