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From the Admin menu expand the Options -->T&E Options menu item
Select Module Enable
Select the “Expire Approval by email link (Default 1440 Minutes)” and update the value
Make sure save the changes
Optional: If you would like the update the message that goes along with the email notification, those can be updated under Admin → Options → Email Message Settings → Time or Expense Email Messages
Select “Approve/reject expense report from email option and update the subject and the announcement part of the setting. Click “Save” to save the changes:
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