I found the following, but it states that Reminder Notifications are reset not the Expiration. I believe the Expiration would remain the same as it was when the envelope was originally sent unless you Correct the envelope and change the Expiration.
https://support.docusign.com/en/guides/ndse-user-guide-send-reminders
If automatic reminders are enabled for an envelope, then resending it resets the time sent for automatic reminder notifications. For example, if your automatic reminders are set for 3 days and you resend a document, the automatic reminder will be sent 3 days after that date, not 3 days after the envelope was originally sent.
Please post a link to the DocuSign article regarding the reset of the expiration date.
Thank you! This was helpful!