Been doing a bit more research into this, the actual permitted IFSD rate to retain 180min ETOPS is .02/1000 flight hours (1 in 50,000 flight hours) while crawling the web I came across this article written by Joseph P Marksteiner who is / was manager of investigations and accident prevention at GE
Also found an article on GE's website dated 22/10/03 stating that that the GE90 had passed 4,000,000 flight hours on the 777. Ill let someone else do the maths, as its 03:35 here. I did them and came up with some scary figures for permitted IFSD's without losing ETOPS status, would like someone else to try and work through them.
Permitted shutdown rate .02/1000 hours - 80,000 engine hours per month - 126 ships in service - 4 million flight hours total - 8 years service.
ARE AIRCRAFT MAINTENANCE PRACTICES TOO RIGOUROUS?
May some current maintenance practices and philosophies be causing more problems than they are preventing? Studies have suggested that nearly a third of in-flight shutdowns (IFSD) are caused by errors brought about by maintenance activities.
Joseph P Marksteiner, GE Aircraft Engines
As aircraft and systems age, the need for preventative and corrective maintenance activity usually increases. "Airlines, aircraft manufacturers and government regulators jointly work out detailed scheduled maintenance programs designed to avoid and catch problems before they become serious enough to jeopardise an aircraft's ability to fly safely… At each step in the process mechanics probe deeper and deeper into an aircraft taking apart more and more components for closer inspection."
This increased level of maintenance activity, while reducing risks due to equipment failure, dramatically increases the risk associated with maintenance activity itself.
Sources
ARE AIRCRAFT MAINTENANCE PRACTICES TOO RIGOUROUS?
GE engines surpass 4 million flight hours powering 777