Of these ex-Soviet ships, the third sister MSC IRIS ex-KAPITAN GAVRILOV is the oldest, completed 6/1982 - all three lengthened in 1989. The 1992 re-engining (why was it, I wonder?) probably nothing to do with the longevity so far, as the two sisters are apparently still running with their original installations.
As expected - and taking container vessels over 10,000gt only - all eleven that are older than MSC IRIS are indeed US-flag vessels, headed by LIHUE, built 7/1971.