Purple Haze:
One of the problems you run into here is that each of the system components (engine, fuel system, etc) is so highly reliable that when you put them together the mathmatics used in the usual reliability calculations of mean time between failure and such become meaningless because (among other reasons) the numbers plugged into the equations are all estimates. This is because it takes so long (calendar time) to develop a data set.
If you are not comfortable with the "9 nines" reliability of the engine reflect on the fact that the navigation system (GPS) has "7 nines" as a design goal (to be demonstrated..it will take a couple more years to collect enough data) so your engine may work but you won't know where you are unless you take along your boy scout compass.