We often get asked by people wanting to switch to using bleach, but already own a tub of trichlor, just how long it will last. Well today I needed a couple of trichlor pucks (CYA and FC a little low, plus needed to lower pH a little), and happened to have an unoppened 37.5 pound tub of trichlor that was bought in either 2008 or early 2009 and stored in a semi sheltered location exposed somewhat to the elements (shelf in screened in BBQ house), I broke the safety tab off the bucket and opened it. I found the desiccant pack had turned brown and looked sort of nasty and 3 of the trichlor pucks had brown soft spots on them the largest spot was about the size of a quarter, the rest looked like new, except for one that was broken in half. The location where the tub was stored is partly sheltered from sunlight, but there was noticeable fading of the printing on the tub, is sometimes exposed to rain if the wind is blowing right, and is subject to some freezing temperatures in the winter, rarely below the mid 20's and highs around 100 degrees F in the summer (southern exposure location). Note these were bulk packed trichlor pucks, not the individually wrapped ones that are more common now.