I did a test a couple nights ago with some new Raka w/350 hardener, year-old MAS w/slow hardener, and some 3-4 year old System 3 w/ 5-6 year old slow hardener. The MAS hardener had discolored significantly, the System 3 to a lesser degree; after all I've read regarding the properties of various brands and hardeners, I was surprsed to find that the Raka set up the fastest. The other two are still slightly flexible, the Raka was hard the next day. I took care to mix each batch for the same length of time.
Do the curing properties of epoxies and hardeners change after a few years of sitting?-Greg