Just to add, the primary failure mode of critical jet engine components is fatigue. To see, and thus learn, from fatigue failures in the field you need thousands of components flying thousands of hours, this takes years or decades. And to learn from this in a way that let's you improve design you first have to get past manufacturing and maintenance induced issues. Which is to say, it takes time to get good at jet engines, on the order of decades when you are talking about the tightest margin sector of the field (big commercial engines).