TSC will issue the EAD effecting upon the completion of the current EAD if the center receives the I-765 within 120 days of the EAD expiration. In cases where the I-765 is filed more than 120 days before the expiration date of the current EAD, the center will hold the application or issue an RFE.
source: http://www.immigration.com/newsletter1/tscup100303.html
source: http://www.immigration.com/newsletter1/tscup100303.html