It is indeed a robust bit of kit.
In December 2003, a second development engine completed 3,000-cycle ETOPS ground demonstration and three 330-minute diversions at GE's test facility in Peebles, Ohio. During the ETOPS ground demonstration, the development engine was the first GE90-115B engine to operate at more than two times the production vibration limits in both the high-pressure and low-pressure systems at multiple thrust levels. This engine is currently undergoing a complete teardown and piece-part inspection to identify leading indicators of durability issues.
From
GE90-115B Completes 11,000 Cycles of its Unprecedented Maturation Program | GE Aviation
However, high N2 vibration (above 4.0 units) has been the cause of VBV actuator fuel line failures including one in flight fire and shutdown.
Page 27 of this report is worth looking at.
http://dgca.nic.in/accident/reports/A6-EBO.pdf