shelf life

[tomstevenson]

I assume that you do not mean how long it should remain in drinkable condition if unopened, which is the usual connotation of shelf-life, but instead you are asking how could its drinkable condition be extended once opened. Because of gas loss, the preservation of an opened Champagne is a bit more complex than that of an unopened still wine. What the two have in common is that colder themperature it is stored at, the longer it will last in a recongnisable condition (providing you do not go to freezing or below, that is). The colder the temperature, the slower the gas is released, but it will dissipate quicker than most of the aromatics in a still or sparkling wine (which is why the fruit will eventually seem to have been stripped from the wine). The only way to prevent that is [i.] to reseal the bottle, [ii.] reduce the amount of air-space, and [iii.] replace the air with CO2 at an equal pressure to that in the Champagne. There are some devices sold to preserve sparkling wines by pumping air into the bottle to make the air-space equal in pressure to that in the fizzy wine, but this not only does not work (because the CO2 pressure in the air-space is hardly effected, thus the CO2 in the wine continues to escape) it actually forces an increase in the rate of oxidation! Theoretically the cheapest way would be to pour the Champagne into a screwtop bottle and seal it with as little air-space as possible, but in practice the bubbling up is such that you lose more gas in the process that you would save.