(WineMag) - The question of how long you can keep an open bottle of wine before it’s past its prime elicits one of two answers: “What? Open bottles? You should drink the stuff!” Or, “Yes, I’ve often wondered!” Here’s a practical guide to know when it’s time to say when.

Still Wines

John Belsham, an international consultant and founder/winemaker of Foxes Island in New Zealand, says, “The ultimate deciding factor is quality. The better the wine, the longer it will keep in an open bottle. That’s irrespective of the techniques used to protect the wine, be it gas-injection or vacuuming…The bottom line is that once you’ve opened the bottle, oxygen is introduced, which is absorbed into the wine. It’s not actually what’s in that space above the wine that makes the difference, but what’s absorbed into the wine at the moment of opening.”

White Wine

“The wine will not rapidly oxidise, if it’s been well made,” says Belsham. “I would expect a quality bottle of Chardonnay, Riesling, Sémillon or Sauvignon Blanc to last comfortably three to four days in a half-full bottle. Really high-grade, single-vineyard wines with a high fill level will last for at least a week in the fridge, in my own experience. Even with slight loss of aroma, it will still be palatable. Mass-produced, simpler whites and rosés are probably best [enjoyed] over two days.”

Red Wine

“With red wine, similarly, it will comfortably be in good shape for three to four days,” says Belsham. “The more robust the red wine, the more tannin it has to protect itself against oxygen. So, the denser the red wine, the better it will present itself. For example, I would give elegant Beaujolais three to four days, but five to six days to a robust southern Rhône or Primitivo.”