Well, it's enough to make 80 GALLONS of sanitizer. Since you can also continue to use it after brew day, there's not much point in dumping it out and making fresh each time. I normally mix up about 2.5 gallons at a time. I keep a spray bottle of it on hand (easy to spray things you need to sanitize) and just keep it until either I've used it up, almost used it up, or feel like making a new batch. I've yet to have a batch around long enough for it to be not effective. Just keep a lid/cover on the container and you'll be fine.