Depends on type of wine and how it was stored. Reds like Cabernet Sauvignon tend to age very well, 20+ years is feasible for a good one. If bottle stored on its side to keep cork from drying out and kept from temperature extremes your wine might be fine. Open and taste. If too old it may have lost its flavor. If you have specific Zaca Mesa older wines, call the winery directly and ask what they think.
Follow these instructions to open a vintage bottle of wine! Allow the bottle to rest on its side so that any sediment, and there will be sediment which NOT an indication of it being bad, can settle to the side facing down. You're going to open the bottle gently at an angle that allows you to not spill but keeping it layed down to try to not disturb the sediment. The cork may be deteriated, this is normal and doesn't automatically mean it's bad. There are these cork openers that have two flat pieces that go arohnd the cork which are best but not easy to use. Once you have the cork out use a light to shine through the neck as you pour into a decanter. Once sediment seems to be flowing in excess to what you're comfortable with you may stop and allow it settle then repeat until youre satisfied. Allow it to decant for as long as is appropriate for the type of wine. You WILL know by smell or taste if its bad. If its good you will likely have a religious experience.
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