As I cleaned my shed, I found a box that was given to me a while back (a few years). The contents of the box include a bunch of snake oil additives, a couple containers of KENT PH adjustment powder, various test kits and two small bottles of E.S.V. B-Ionic 2-Part Calcium Buffer (#1 and #2). Both bottles are half empty. I can't seem to find a date on either of the bottles. Do these stay good?