Not specific to PS23x, which is obviously named for a brand of deodorant-antiperspirant... or a public school in Brooklyn.

I store all reagents in an unconditioned space (a closet) -- but not in the garage or an out building, in order to protect them from heat/cold. My understanding is that acids (sulphuric and the like) will hold up for years and years. That’s forever in my book. FAS-DPD components (like the R-0871 titrant that comes in a suspiciously darkened container), however, are pretty vulnerable.

Someone on this board buys a quarter pound (or maybe a full pound?) of DPD R-0870 powder, wraps it in plastic and stores it in her refrigerator. (It just sits back there next to auntie's Prune Salsa, a gelatinous cube of preserved fruit, circa 1965.) I think I'm going to start purchasing DPD powder this way—just as soon as I use up all the pesky 10 mL vials I have scattered about the house.

And more calcium indicator. You can never have enough calcium indicator. I have the quart size. That's good, but I’m going for the gallon next time. It will really impress my neighbors, who have to live with puny 3 /4 oz titrators.