It's important to make a distinction between RMS (rear main seal) oil leak issues, which has generally been cured with the latest generation of seals and the "bad casting" and "crankshaft" problems which caused real engine failures with the early 3.4 engines.
Of course, engines do fail from things that are not actual "flaws" with the engine, such as overreving, running without oil (as one mechanic told me after a customer came down hard on a speed bump in a 996 and cracked the bottom of the engine, allowing all the oil to leak out), etc.