I called the Canadian Nexus Centre in White Rock. They told me that the standard of service for the US review is up to 7 months from the date where the application was referred to them. They told me that my application was approved by Canada in 2 months after submission in September, then was referred to the US for their approval and they have 7 months to approve it. So doing the math, it seems that the application could take up to 9 months for conditional approval.