This is the main part:
How will USCIS decide whether to issue an EAD valid for one or two years?
USCIS will decide whether to renew an EAD for either a one or two-year validity period based on the most recent Department of State Visa Bulletin available at http://travel.state.gov/visa/frvi/bulletin/bulletin_1360.html. If an applicant’s visa number has retrogressed and is unavailable, USCIS may issue a renewal EAD valid for two years. USCIS will continue to issue the EAD in one-year increments when the Department of State Visa Bulletin shows an employment-based preference category is current as a whole or the applicant’s priority date is current.
How will USCIS decide whether to issue an EAD valid for one or two years?
USCIS will decide whether to renew an EAD for either a one or two-year validity period based on the most recent Department of State Visa Bulletin available at http://travel.state.gov/visa/frvi/bulletin/bulletin_1360.html. If an applicant’s visa number has retrogressed and is unavailable, USCIS may issue a renewal EAD valid for two years. USCIS will continue to issue the EAD in one-year increments when the Department of State Visa Bulletin shows an employment-based preference category is current as a whole or the applicant’s priority date is current.