Increases turbine life, sure, but what about compressor blade vibration??
Well, if significant flutter on the trailing edge of the exhaust is a symptom of vibration in other areas, then the 400's definitely have a problem.
I watched the Stbd engine exhaust on a flight from DUB to EXT a while back, and from about 15 Ft after take off until touchdown, there was a significant flutter on the exhaust on the inboard edge, covering an area of about 15 Cm, and fluttering over probably 1 Cm either side of normal position.
It was more pronounced while flaps were deployed, but still continued after power reduction in the climb, and in cruise and descent.
I would be concerned that an ongoing flutter of this magnitude is going to lead to stress cracking sooner rather than later.
Maybe it's not significant, but it's certainly disconcerting to watch, particularly when it's constant.