Think about it: this is a luxury problem. We have so much clean, safe water that we debate its shelf life. That’s a reason to celebrate! And knowing the basics means you can laugh at old bottles instead of worrying.
So next time someone panics over a days-old bottle, just smile and say, “It’s fine—water doesn’t hold grudges.” You’ll sound wise, and you’ll save them from pouring perfectly good H2O down the drain.