I have quite a bit of flourite in the garage taken from one of my tanks, about 2 years old. Wonder if it might have lost some of its potency during that time span, and whether it would be best to add some new/or other type of substrate material to the mix? All comments appreciated.

Should be ok, I'm told it doesn't lose its potency. Just rinse it, first, before
using. If memory serves, this is what Greg Morin of SeaChem posted to APD.

Bill