I am using the Rollie c-41 chems and have had no problems mixing them in my Jobo plastic cylinders or using any of the various plastic graduates I have. Now I clean them right after use but so far no issues. I also use Argon to purge all my concentrate bottles and have had some last for well over a year. I do this with C-41, E-6 and B&W chems. I don't know about working strength as I mix everything one shot.