I had been using the Tetenal C-41 kit, which seemed to work fine. eventually the developer died, though it was mostly all used up by then. I recently switched to all Kodak chems for C41, with separate bleach and fix. At first glance the negs seem better - just slightly clearer and better, it seems. Hard to say for sure without denisitometry but it just seems like they are better than the Tetenal Blix C41 chems. As a bonus the kodak chems are cheaper per roll I think. (the hazmat shipping is a killer though! Almost doubles the price on some parts of the chemistry.)
I use a Phototherm SuperSidekick 4 which uses 2 oz. (60ml) of solution per run, plus 3 ½ oz. (105 ml) per roll. It can do 4 rolls at a whack so 4 rolls of either 35 or 120 uses only 480ml of chems. I use them all one-shot except I save the bleach to regenerate it for reuse later.
I mixed partial amounts of the developer, and tried to tightly seal the concentrates using inert gas, we'll see how they keep. Hopefully well.