Many of us never reach this situation as we polish off a bottle (or more) the first day we open it! I love to drink wine almost every day, but not that much. And if it is just my wife and me, we may want to share a bottle over a few days. Given what we have for dinner, what wine is leftover may not go with the meal the next night, so I may open another bottle to better match the food. Then I may have two or even three bottles of open wine sitting around!
There are several ways to store wine and keep it reasonably fresh and drinkable for several days. I use the Vacu Vin pump and stoppers. Similar models are made by ScrewPull and others, but they all basically work the same. The newer models have a clicking sound to alert you that you have pumped as long as required and have removed the air from the bottle. Make sure you get the newer model! It works far better than the old ones. The newer stoppers look like the ones to the left. The older model stoppers look like the ones below and to the right.
I had opened a 2005 Stags Leap Black Label Petite Shiraz a full week ago, and because of the meals we had during the week, I did not get around to drinking more of the Stags Leap until last night - six days after the bottle was open. It was still very fresh, and tonight I am finishing off the last of the bottle. It has very slightly diminished in freshness, but still an excellent wine.
I should point out that lasting a full week has to do with the quality of this wine. It is about $60 - $75 per bottle in Australia and has been built to last. It is unusual for a wine to last this long in an open bottle when using the pump and stopper method. This is the sign of a very good quality wine. Most wines in their optimal drinking range will be good for two to three additional days at the longest after opening the wine. Once a bottle is open, you should always try to drink the wine within one or two more days after opening. Better quality wines in their optimal drinking range should be able to last two to four days, but I would not normally push it beyond that. I was lucky with the Stags Leap!
A great, big wine with some age on it will mellow and may even be better after another day of being opened. This was certainly true of the 1987 Pyrus I discussed in another post entitled "Should you decant wine?" This wine tasted better the second day.
However, you need to be really careful with older, more fragile wines. The structure is much less tight than for a newer wine and will break down quickly. An older wine should be drunk in its entirety the same day, or certainly the next day. It will lose flavor quickly and have noticeably deteriorated by the second day.
To use the pump and stopper, place the stopper into the bottle completely flush, and then put the pump over the stopper, holding the pump down onto the stopper to provide a seal. Hold the base of the pump with one hand and lift the handle of the pump up and down until you start to hear a clicking sound. This will indicate that you have removed the air from the bottle. Do this each time you open and then close the bottle. As the wine in the bottle becomes less and less, the amount of time to remove the air increases slightly.
This process will allow you to get more enjoyment out of your wine, even if the bottle has been open for several days. Drink well!
(BTW, this process is not necessary for fortified wines (alcohol over 20%) as the air does not create the bacterial effect it would with wines which are 16% alcohol and under. You may just stop up the wine with the original cork. However, make sure to stop the bottle somehow as if left open, while not turning to vinegar, a fortified wine will still lose flavor.)