One thing to bear in mind is that, as mentioned before, the engines were designed for use in power stations, running on gas, where they'd run at constant speed for prolonged periods. While in rail use, they're starting and stopping frequently and alternating between full power and idling all the time; I think it's been said that rail use is perhaps the toughest environment you can get, since you're either idling or at full power and switching rapidly from one to the other. Perhaps GE might have beneficially put a prototype engine in something to thoroughly test in first in real working conditions, rather than (as I presume they must have) on a static test rig.
