I just finally used up and threw out a set of cans of EA 40 I bought in 2010.....I subject them to extreme temperature variances over the years...moved them across the US and back and the stuff has still been working well for the little, non-critical epoxy projects I would use this old EA 40 for (i.e. gluing random stuff in the garage and gluing up hidden tang knives, etc.).
I can tell you that it definitely become less workable after a year, but still useful - so don't throw out your old stuff....just don't glue up a nice bow with it!