I'm actually a mix from scratch c-41 guy, which makes me an outlier. I have nothing against kits, but have heaps of bulk dry chemistry from b&w, so the idea of colur mix up's don't scare me off.
Developers are the most fragile; most don't last well once mixed, and last even less time once partially used. I currently have 8 reels of films loaded ready to go in the c-41 chems that I plan on mixing tonight, tempering starting tomorow morning before I go to work, and processing tomorrow night. I am extra strange; I developed a c-41 replenisher to keep uniformity as the solution is re-used on subsequent batches
I quit color developing because of too many lost rolls.
If you have a method of brewing C-41 developer I am another who would like to see it.