I always mix the RA/RT per daily session, or even per print. That has pretty much ended any questions of predictability,
provided one isn't down to the last bit of concentrate and has temp under control. Never had much luck with other brands, but haven't tried some of the more recent options either. If Kodak tanks, someone will still provide high quality RA4 chem, because it's essential for both traditional dkrm use and all the digital laser printers like Lightjet. My only question at this point is whether to install a 40" roller processor instead of using drums. And unfortunately, it's the kind of gamble that depends on the continued availability of 8x10 color neg film and matching C41 service. The good new is that at the moment, Fuji seems to be stocking more roll sizes of Supergloss in the latest CA II.