For sure a cell can short suddenly and kill the battery. Can happen to a new battery also - my record is 6 weeks on a Nissan OEM battery - whomever made those back in the day. Also had a couple Walmart batteries fail pretty early as well.The battery testers are nice. I try to test mine every oil change at minimum.
That said, I'm hesitant to rely on them with much confidence. I've seen batteries pass the test during an oil change only to fail a couple months later. Older battery, pass or not, seems I would still consider replacing it if finances allowed.
Admittedly, there could be something I'm doing wrong or do not understand about the process.
Still - nothing wrong with replacing batteries every few years.