I read that calcium hypochlorite will last a long, long time. I guess this depends on storage conditions tho.
I had a few of the military water purification kits in the glass vials with test strips etc, but dumped most of them a couple years ago. I just found another one in a bag I had stuffed in storage, and was wondering it it might be of any value.
It was made in 1991, and has been in a hot/cold storage unit for 20 years. Would it not be worthless due to temps and age??

Katadyn,,micrpur

https://www.outdoorgearlab.com/reviews/camping-and-hiking/backpacking-water-filter/katadyn-micropur-purification

I used the military stuff while deployed with USMC in the 80s.  It does get weaker with age, temperature and humidity.  Both the Cl and the testing agents.  The Cl especially if the containers have been opened.