I will second the coment s on long lived RA-RT. I too run a CP31. I have a bottle of the low utilization adder for blix that likely helps me store the stuff a long time.
I do filter the blix if it is used, and has sat a long time (like more than 3 months), to make sure it is not sulphuring out before pouring it back into the processor. I store it in a 2L palstic bottle.
The developer I store in a 2.5L glass bottle, and gas blanket it, to keep it from oxidizing.
I do not sure used solution with new solution in the same bottles. If I need to replensih from the last session, I won't do that until I start using the chems again; that way some fresh chems get into the tank every time.
I have had good results re-using RA-RT for periods of over 4 months. The used and replenisher solutions are stored in a 16-20C basement in the dark.
I mix replenisher 1L at a time. I seem to recall with the kit I buy from Kodak I worked out that it is 50mL A, 23.6 ml B, and 50mL C per litre.
I do repour the B developer component when it first comes to me into a small glass bottle(s) and gas top them as well if they are not tolally full.
Things last much longer this way than mixing the whole 10L at once.
I too concur with the blix contaminating the developer theory. It does not take much to mess it up.
I don't pull my racks until after I have drained the processor, and then refill the tanks with water for a rinse, hoping that this keeps the chance of contamination down.