At a former airline of mine, it was stated they never had an engine failure using "flex" (standard, reduced, etc.). The only engine failure I have had at an airline was a TOGA T/O, we didn't need to do it but the captain (and he is the captain) wanted to use it. We got to 60 knots when the #3 blew every blade out the back.
Long story short, back to the gate, looked through the engine from one end to the other, seeing daylight all the way, and commuted home, taking 12 hours. That was our last leg of a five day trip.
I am a firm believer in flex because I like to be gentle with my tools, take care of them and they take care of you.
