From June 20, 2014, the US FDA Stability guidance for ANDA submission will require 3 batches for every strength (three industrial scale or two industrial and one lab scale) and 6 months of accelerated stability
Note: If 6 month accelerated stability show significant change and failure of any attribute, 6 month of Intermediate data are also recommended at the time of submission
http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM366082.pdf