the link

http://www.murthy.com/news/n_favint.html

Previously Approved Advance Parole

The USCIS stated that if a person has an advance parole and applies for a new advance parole while in the United States, s/he may travel and reenter the U.S. using the already approved advance parole. The person must return during the time period permitted under that advance parole that was approved before the person's departure. The USCIS specified that the person cannot remain abroad after the expiration of the first advance parole and then seek to enter on the second one after it is approved.