The UCC does not require you to send statements at all...but if there is a fraud question, the accountholder is not subject to the notice requirements in the account agreement because they did not get a statement to review. To answer you question, the UCC does not require you to keep sending statements to a bad address, and if it is not a bad address, it is not a dormant account.
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Better a patient man than a warrior, a man who controls his temper than one who takes a city