When your bulk order of ajwain arrives, you should store it in a glass jar with a well-fitting lid. It will keep fresher if you store that jar in a cool place. Kitchens tend to be warm, so consider keeping a small jar of ajwain at arm's reach in your kitchen and putting the rest in a cooler place for long term storage.

http://www.traditional-foods.com/profiles/ajwain-seed/