Ilford does not give information regarding the number of films that can be fixed per volume of fixer, and Terry's advice accurately reflects their recommendations. I always mix 2 liters of rapid fix and never fix more than 40 rolls of film in it. I put a piece of black tape on the bottle and make a mark on it for every roll I process. For my purposes, each mark counts as one 8x10 piece of film. One roll of 35mm, one roll of 120, or four sheets of 4x5 equals one sheet of 8x10, equals one mark. Ilford states that as the fixer is used, the fixing time increases, but I've always simply used 2 minutes (exept for T-Max, where I use 3 minutes). This is a very conservative use of the fixer, as Kodak states that their rapid fixer (1:3) will fix 32 sheets of 8x10 film per quart. Kodak also states that the 1:3 working solution will keep for two months in a stoppered bottle.(posted 8684 days ago)For paper, I use two fixes, each of 2 liters, the second fix becoming the first fix after 60 8x10 prints (or equivalent).
In regard to Kodak indicator stop, Ansel said that by the time it changes color it has ceased to be an effective stop bath. So I use acetic acid, as it is cheaper. We have a dealer in town that stocks the glacial, so that is what I buy, as it is MUCH cheaper. A gallon of glacial acetic acid will last me several years.