See details here

Your attorney is right for the regulations of U.S. C.I.S. state that after the 6
year initial admission has expired, further extensions will be granted
in 1 year
increments. But you could be an exception and may be available for 3 years
increment because of the following reasons:

1) From USCIS press release on 7/23/2007, Q17 says:

Q17: How will USCIS interpret the language of AC21 Sec 104(c) (for
three-year H-1B extensions) during a period in which AOS applications
could be filed?
A17. USCIS interprets AC21 §104(c) as only applicable when an alien,
who is the beneficiary of an approved I-140 petition, is eligible to be
granted lawful permanent resident status but for application of the per
country limitations. Any petitioner seeking an H-1B extension on behalf
of a beneficiary pursuant to AC21 §104(c) must thus establish that at
the time of filing for such extension, the alien is not eligible to be
granted lawful permanent resident status on account of the per country
immigrant visa limitations.

The whole page is here:
http://www.uscis.gov/files/pressrelease/EBFAQ1.pdf


2) You're China (mainland-born) citizen and PD is not
current for I-485 processing from the visa bulletin in May
(Employment-based 2nd: 4/1/2004) even though you'vefiled I-485.

http://travel.state.gov/visa/frvi/bulletin/bulletin_4205.html