I have been following developments in vibration monitoring for thirty years. Works great in large static machine installations, not quite so well in complex highly mobile vehicles that are subject to constantly changing external conditions.
Hindsight being a wonderful thing, I can easily envisage that certain signs were picked up in advance of the failure but not recognised for what they were because they appeared "normal", or were buried in the noise.
I am still also of the opinion that there is something different about North Sea operations compared to other areas. Whether it is weather conditions or long passages with relatively constant power settings followed by high energy manouvers to land, or some other factor, I don't have any evidence to say.
Living only a mile south of Norwich International Airport I do get to see an awful lot of helicopter movements every day. Fascinating machines, but you wouldn't get me up in one!