It has been my experience that a half full bottle of wine will remain at peak or even improve for 12-24 hours after simply being corked and placed on my kitchen counter at 70 degrees Fahrenheit. After that, the wine tends to jump off a cliff rather rapidly, say in another 24-36 hours.
That same wine placed in the fridge sees about a doubling of each time stage, still at peak or improving for two days and drinkable for another two or three.
Pour half of the bottle into a half-bottle, cork it and place it in the fridge and you’ll end up with an almost new bottle, one that you can revisit for weeks and still thoroughly enjoy. I’ve even found a bottle a year later, don’t ask, and it was still delicious!
Photo courtesy josewolff