According to the insideevs.com monthly scorecard, sales began in earnest in May-June 2012. Frankfurt is in September-October, so about 2 1/2 years later. But remember that the FFE has the advantage (contrary to what the purists would maintain) of being built on an established platform. This almost certainly reduced the risk and the issues to be resolved.
2013 FFE Returned after 3 years with 52,000 miles and battery down to 15.2 kWh
2014 Volt returned with 43,000 miles
2014 Volt 26,000 miles
1967 Corvette 427
1962 Corvette 327
Awaiting a Bolt