I can't answer on how long the mixture will keep. However, you probably don't need to be doing this thorough of a cleaning on a regular basis. I do it about once a year. Actually, I didn't do it at all last year. I rinse my cartridge when the filter pressure gets 10psi above where it's at when clean. That's just a (reclaimed) freshwater rinse with a hose and a spray nozzle.