The shelf lives of different chocolates vary. If stored properly, unsweetened and dark chocolate can last for about 2 years. However, you should count on milk and white chocolate only having a shelf life of about 6 months because of the higher sugar and fat content. Be sure to put a date on any chocolate you store so that you can keep track for future use.
Wrap any open bars in plastic wrap and store in a cool pantry for maximum freshness. If the chocolate gets exposed to rapid changes in humidity or temperature, the fats and sugars may soften and discolor the surface. If this happens, don’t just toss the chocolate thinking it’s no longer usable. It’s still good. Just use it for cooking or grating. The technical cooking term for this is called “bloom” and it doesn’t affect the chocolate’s flavor.
Also, it’s important to remember not to store chocolate in the refrigerator or freezer because cocoa butter absorbs the flavors from other foods and it changes the chocolate’s crystal structure and the way it reacts when used in different recipes.