Think of water in plastic like a couch potato. It’s fine doing nothing for a long time, but it doesn’t get better with age. It’s not wine—it’s the opposite of wine. Wine grows rich and complex; bottled water grows flat and hollow.
Or compare it to a library book that nobody reads. The book lasts forever, but the cover gets dusty. Your plastic bottle is the same: the water is the story, and the plastic is the cover. After a decade, the story is still there, but the cover might be crumbling into your lap.
Another way to see it? A full bottle of water is like a time capsule for your thirst. Open it too late, and instead of a satisfying drink, you get a science experiment. Would you drink from a time capsule from 2019? Probably not unless you’re a very brave (or very desperate) archaeologist.
How Long Can You Keep Water In Plastic Bottles at Albert Hoopes blog