you're probably OK without getting renewed consent
I can go as far as "probably", also.
A valid ESIGN consent must occur "...in a manner that reasonably demonstrates that the consumer can
access information in the
electronic form that will be used to provide the information that is the subject of the consent." Clearly, you're OK if you don't change the "electronic form" (file format), but the other part--access(ing) information--gives me a bit of concern. When the customer gave consent, s/he proved s/he could access an attachment to an email message. S/he did not demonstrate the ability to go to the proper section of your home banking system and pull a file.
The OP didn't indicate that the statement file format would remain unchanged and may have a different situation.