Vinegar Is Nearly Immortal in the Pantry
Vinegar is already the product of fermentation gone as far as it can go — acetic acid at that concentration is too acidic for most spoilage organisms to survive in. A sealed bottle of vinegar kept in a cool, dark pantry will keep its acidity essentially indefinitely, though flavor can mellow slightly over years and a harmless cloudy sediment (called "mother") can form in unfiltered varieties. There's no real need to refrigerate any type of vinegar.
Sources & methodology: These tips draw on established food-science references —
Harold McGee's food-science writing, America's Test Kitchen /
Cook's Illustrated testing, Serious Eats'
technique reporting, USDA food safety guidance,
and peer-reviewed food-safety research (including UC Davis
cutting-board studies) — not reworded recipe-blog consensus.