Sorry I don't have an answer, just tagging along. I have quite a bit of salt from the 2002 and 2003 vintages. I'll mix it up and let you know how the parameters are. I used one old bag that was open for years and the pH was really high (over 9). I still added it (new tank) and the pH came down to below 8 -- all readings using pinpoint pH meter.
The only possible issue is that some of the calcium may not go into the solution due to reaction with moisture in the air. You may need to increase the calcium and alk. a bit after mixing. Other than that, it is fine to use.
