Keep it in the fridge.
We did a tasting last Sunday week for a customer who was trying out wines for a function or something and what can you do but drink the open bottles? So I whacked them in the fridge and drank the last one 6 days after being opened and it was fresh as a daisy. So, what were they?
Monday - Prosecco La Riva dei Frati, bubbles kept intact by their own champagne stopper, this always hits the spot. Fresh, fruity and delicious.
Wednesday - Degani Valpolicella 2007. Aldo's wines get better each year. The 07 has the typical cherry fruit, but with more guts and body than previous years.
Thursday - Nautilus Sauvignon Blanc 2007 - good, benchmark Marlborough Sauv Blanc.
Friday - Gruner Veltiner Terrassen 2007 Domaine Wachau - again, very fresh, a really good example of this popular Austrian varietal - good value too.
Saturday - Tussock Sauv Blanc 2006 - arguably a year older than it should be but all the better for it as it is showing some unexpected complexity. Drinking really well!