“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
I've been using TF-4 for years for my films. Great stuff! I do two one minute constant agitation rinses as a stop. After mixing up a gallon of working solution, I pour just enough for the format of film I'm working with: 250ml for 135 film and 400 ml for 120 in a 16oz steel tank. I fix three rolls and discard and use a fresh quantity from the gallon of working solution. I'm probably well off in not stretching the capacity but I feel better by not trying to economize by pushing my luck. Fixing is so important and since TF-4 is $10.99 a bottle at Freestyle it's worth knowing my negs should be stable for many years to come.