I've never heard of a shelf life on calcium media. The media I'm using is running on the two year mark and it still test fine and dissolves the same rate as when I bought it new. I just happend to buy 4 buckets of arm at a very cheap price so I'll be running that for sometime. The only thing I do is every 6 months I remove the very small particles and rinse the media to make sure there's no detritus or anything that can shack loose and shoot though the pump. I also top off with media at the same time and while the reactors apart I calibrate the pH probe.
