If I look at the
MSDS for Unicolor's powder kit, I see that BLIX part A consists of mostly Ammonium Thiosulfate, and then Sodium Carbonate. This tells me that the resulting solution will be quite alkaline, and as a result I expect it to release Ammonia over time. Also note that it likely contains no (or only very little) Sulfite.
If you can get the Ammonia smell under control (tightly sealed bottle), then you should be able to make a stable BLIX A concentrate. Ammonium Thiosulfate is very soluble (600g in 1 l), Sodium Carbonate is also well soluble, so you shouldn't need much water. Higher concentration usually means better shelf life.
Unicolor's BLIX part B contains, according to its MSDS, Sodium Ferric EDTA, Sodium Sulfite and PDTA. There is a chance that the Ferric EDTA will oxidise the Sulfite over time, and that this BLIX part B, mixed as concentrate, will not outlive regular BLIX by much. Making a concentrate doesn't help here either, because the reaction doesn't involve aerial oxygen, but reactants within. Note, that liquid concentrates put the Sulfite into the fixer component, not the bleach component, probably for good reason. Also note, that this Ferric EDTA plus Sulfite effect would not really hurt in a bleach, since the bleach doesn't need Sulfite, it's the Thiosulfate which needs it.
My recommendation would be that you mix the whole thing at once, process as many rolls as you get around to while the BLIX lasts, and then continue your journey with liquid concentrate kits.
