It took them 6 months to process my EAD about two years ago.
I called 1-800 three times after the first three months waiting, and was told that my biometrics were not current. The 1-800 issued three service tickets to request USCIS to mail me biometrics appointment notice. Got nothing from USCIS. Had to wait 30 days after each ticket.
Then I went to the infopass and got help from a nice lady, who set up a biometrics appointment for me next day and filed request (complaint) via email, internal phone call and fax. Apparently, they do have a direct inter-office line between the infopass and the USCIS. Basically, she told them that my biometrics results are on the way and they should expedite the process. That infopass lady - officer Joans really has sensitive and sweet heart. Finally I got the Approval notice about 10 days later - 3 days before my EAD was expired.