My iPhone 6 was released on September 19, 2014 and it received its last OS update on September 17, 2018 with iOS 12 so it received only 4 OS updates updates. It continued to receive minor security updates until June, 2021 so about 6 1/2 years. Although, the security updates it received after 5 1/2 years were minor and not comparable to the full updates non EOL devices received.