People get too hung up on this. If you already ran 12 hours a day, it's only another 12 hours a day for 84 hours a week extra off the 10k hour lifespan. Nobody will ever know their cell died 3.5 days early a couple years from now.
Yes turning the cell off saves lifespan, but not in a remotely appreciable way.
Cell hours are far cheaper than the equivalent liquid chlorine so you flat out win there.
That being said, in the beginning of a swamp battle the SWG can't come close to keeping up, then it quickly makes more than they need a couple days in when it shifts to a mechanical / filtering battle. It makes tracking things more difficult for newbs who are likely already overwhelmed so eventhough it works on paper, it's still recommended to turn it off.