You don't have to wait for an email though. As long as you check the Prime forum at least once in the middle of the month you will never miss out on the free offerings & coupons.

Many stores offer limited free items, some for only a week at a time.

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I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.
-Galileo