One thing I do w/my henna is place it in a sealed plastic zip lock bag and label it with an expiration date, calculated one year from when I received it. Apparently henna powder that's been exposed to the air and/or will last at least one year if kept frozen. Unopened and frozen, henna can last some number of years (uncertain how many).
Got this info from hennaforhair.com
Last edited by Korkscrew; 01-08-2013 at 03:08 AM.