After your film is developed and fixed you use hypo clearing agent to get the fixer out of the film. It’s not as important with film as it is with paper, in fact I never used to use it for film when I was doing film photography, only for paper. Film doesn’t absorb much of the chemicals, so you can just wash it for a few minutes and it’s fine. Paper has to be washed much longer, so hypo clearing agent saves water.

You can use it over and over, but I’m not sure how many times. It’s probably in the directions. Every time you use it it gets a little watered down.

Once it’s mixed up I’d say it would last a long time, maybe a few months.