What I have seen recommended and continue to use for my personal use is to start with fresh chemicals for the first print and save the chemicals. On the second and continuing prints I use 1/2 new with 1/2 used. I haven't noticed any problems but I have not put a densitometer on the prints to verify equality, only used my eyes. It basically doubles your capacity. If it is for someone else who's paying you, I would use fresh stuff
regards
Erik