Posted 17 December 2012 - 03:43 PM
OP what year is it? Is it non-vintage?
When you do open it, take a look at the cork. If it has split, shrunk, has a line or leak running up the side of it, or is visibly moldy then consider the wine effed.
If the cork looks ok then smell the cork, if it smells musty or kinda like wet cardboard then the wine could possibly be affected by cork taint. That's TCA, technically. This is the main reason why most Aussie wines are bottled under screwcap these days - to avoid TCA contamination (which comes from the cork). There are various statistics but most agree that about two bottles in every dozen were affected by cork taint when we were using cork. In the worse case, cork taint is very obvious as the afore mentioned musty, damp character on the nose and palate. In milder examples it can be difficult to detect, it can just deaden the fruit and make a wine look flat and dull. But having said all this, having a wine under cork (ie your bottle of sparkling) doesn't automatically mean it will be off. The only way to find out is to open it!
White wine can age very well, depending on variety and style. For example aged Riesling and Chardonnay can be superb, complex, interesting wines. Ive had sme amazing aged Hunter Semillion. On the other hand, a Sauv Blanc should be enjoyed within about two-three years of its vintage (it just won't look it's best, it won't make you sick or anything!). Sparkling wines can also be fantastic with a few years in bottle.
Another option is to call the winery it was made at and ask the winemaker. If he/she is not out drinking beer I'm sure they would be able to help you, they might even be quite interested to see how the wine is drinking themselves.
Have fun with it, I love opening a mysterious bottle!