Storing Wine After It's Opened
Wine deteriorates in the presence of oxygen. The most practical thing to do is finish the wine. When this isn't sensible, the idea of buying smaller bottles (or taking home unfinished bottles when drunk in a restaurant--you don't have to leave them--though in California, make sure you take it home in the trunk of your car), when available, can be a better solution. You can cook with leftover wine, or even turn it to vinegar (why buy when you can have homemade?). Also note that some young, tannic wines might actually taste better the next day.
But, there is always the time when you want to try to preserve the quality of the wine for as long as you can. To do this, you want to prevent as much oxygen as you can from getting to it.
One of the better ways is to fill the bottle with an inert gas. There are several different systems which do this, but they tend to be relatively to extremely expensive. Nevertheless, for the serious aficionado, this is probably the best solution.
Another product, theVacu-vin (tm) is a small pump device that comes with rubber stoppers and a small hole in the middle of the stopper. The idea is that you can suck a fair amount of air from the bottle, thus reducing the effect of oxygen. Some, but not all, people feel that it might add 2 or 3 days to the life of the bottle.
Other cheap and interesting ideas: Get a bunch of glassmarbles. Clean them, then put them in the bottle until the liquid is to the top, then cork. Or, just transfer the wine to a smaller bottle. Or both.
Initially I wrote "one economical wine lover suggests freezing as a means of longer term storage. I haven't tried this and probably won't; freezing should alter the character of the wine. Cooking with leftovers is probably a better bet."
However, there have been a fair number of people who claim positive results with the process--not only with freezing, but even by nuking the wine (gently) in a microwave to thaw it (at least part of the way).
These people very happy with the results. A few have noted that in some wines there are radically increased precipitates, mostly potassium tartrate. (Increased precipitates result because the water freezes at higher temperatures, therefore the concentration of alcohol and soluble items--such as potassium tartrate--are higher in the liquid portion [the water turning to ice]. Things which will precipitate out easily, will do so, and probably won't dissolve back into the wine so quickly. Now, one possible effect of this is that a wine will taste less acidic--which may or may not be a desirable effect. Another effect is that the constituents of the wine which make up taste and color can be affected. But then, if it works for you . . . .
I think I'll still stand by my original statement that "generally speaking, most stored wine, no matter what you do to it, won't be as good as when you opened it." Nevertheless, those who like the idea of freezing wine seem to think it works better than most of the other storage methods.