I use the Unicolor powder kit, mostly because it's cheap but also because it's easier/smaller to store, and I assume it keeps longer than liquid concentrate.
Here are the things I do to ensure that the dev stays as fresh as possible:
1. Keep it in an air-evac container so that there is very little surface area exposed to air.
2. This container is solid black, so it keeps out light.
3. I store it in my kitchen cabinet, which is also dark and is only opened to take out chemicals (B&W as well as color).
4. I keep all hardware for dev & fixer separate (flasks, funnels, mixing rods, etc). I even keep those hardware items physically separated by a few feet at all times.
5. The only items which sees both dev & fixer is the developing tank, and I wash that religiously after every dev cycle. A forumite was present one time that I developed and said that he doesn't even wash his dishes that thoroughly 😂
Despite this, my dev always dies within about a month, no matter how little I use it (these days, it's once every 3 months or so, so I literally get one dev cycle out of each batch).
My next step is to keep the dev in the fridge to see if it's the temperature that is killing it.
Any other suggestions? 😢 At this rate, it would be more economical of me to get my color film lab developed 😢
