Small turbo-props seem quite prone to shut-downs, don't they? Maybe it's because of the operating environment most work in.
My phone has rung twice in the small hours after double-engine failures in twin-engine aircraft I was responsible for, engaged in civil air transport operations.
By the way, "mean time between failures for the PT-6 is 346,000 hours" does not mean that each engine can be expected, on average, to operate for 346,000 hours without an unplanned shutdown (aka failure).
That statistic is perfectly consistent with various pilots' experiences described here of multiple failures in relatively small numbers of hours, presumably with all the PT6 variants.
I'm sure that there's someone here who can explain the interpretation of MTBF data, and its relationship to real operations, better than I can. All I know is that it makes me very wary about being in a twin over large expanses of water/inhospitable land. (See above re phone calls).