The key to preserving leftover wine is to prevent exposure to air. Air causes wine to age and the wine will oxidize and lose its freshness.
There are devices available on the market that will help to purge the
bottle of oxygen. Canisters of nitrogen can be sprayed into the bottle
before re-corking to displace oxygen. Another device pumps air from the
bottle and seals it with a rubber gasket. These devices help to preserve
the wine longer than simply re-corking the bottle and storing them in