Shelley Young, chef and owner of The Chopping Block, a cooking school on Chicago's north side, cannot stress enough the importance of grinding and crushing herbs and spices. She compares their freshness to that of freshly ground coffee versus canned coffee. Even though it may be more work, there is a distinct and fresh difference which is worth it. Storage Spices such as cinnamon sticks, cloves, and peppercorns have a long life, but you should pack away freshly ground herbs and spices immediately in order to retain their flavor. The smaller the herb or spice is ground or crushed, the shorter its life, since more of the surface of the vegetative material is exposed, which increases the speed at which essential oils evaporate.
Heat also hastens flavor loss.
Keep herbs and spices away from sources of intense heat, such as stoves, sunlight, and high humidity. Never shake out herbs and spices over a steaming pot where moisture and condensation form. Instead, measure away from the steam. For the same reason, never dip a wet spoon into your spice jar. To keep the essential oils trapped safely in dried herbs and spices, use airtight containers and keep the containers in a cool, dry, dark place.