We can only push USCIS once per half year?

Our Case NIW:
March 2005 I-140 and approved.
April 2005 I-485 ted.
May 2005 1st finger print
Nov 2006 排期 current
Jan 2007 Lawyer requested status from USCIS
May 2007 2nd finger print

I heard most people received their GC within one month after 2nd finger print. But we are still waiting...... And lawyer said they can only request status from USCIS once per half year. Is that true? Can we contact USCIS and push them directly? Should we wait for half year per push?

Thanks in advance.