I keep mine hung up all the time, deployed or not.
i've always wondered that too...sorry i'm not much help. :)
I'm not sure about the answer to your question BUT I received my flag in the mail today :)
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So, I guess there are DoD regulations on this, this is what one says: A service flag approved by the Secretary of Defense may be displayed in a window of the place of residence of individuals who are members of the immediate family of an individual serving in the Armed Forces of the United States during any period of war or hostilities in which the Armed Forces of the United States are engaged. Sounds like all the time. It's kind of tradition in my family that the blue star flag goes up the day the service member leaves and comes down the day they are safely home! I think you can leave it up if you want though :-)
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