My answer on this would be 'it depends'. Red wines handle about 4-5 times the amount of oxygen as a white wine before spoiling. Actually, many red wines improve with a little oxidation as one poster mentioned. Keeping things cool will help prevent spoilage as well.

Another factor is how much is left in the bottle? If there's half a glass left in the bottom and the rest is filled with air then it'll oxidize pretty quickly, whereas if the bottle was mostly full you're in good shape. You can drink a glass and put a bottle of red back in the fridge for a week and when you try it again it will still be good.

If you want something that you can just grab a glass once a night and it will stay good I'd highly encourage you to investigate some of the premium box wine options. And yes, that's not as much of an oxymoron as it used to be. Box wine will stay good for weeks or months because the collapsible bag keeps the wine tightly sealed from oxygen.

-TK