Gouli
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.
With 30+ years flying and operating helicopters in most parts of the oil and gas world, I disagree with you. When distance is taken into account, long range operations have basically the same flight profiles and short range have basically the same flight profiles (and HUMS readings) worldwide.
I am sure that you know that the helicopter operations on your "doorstep" is short range different, and lots of landings and take offs. Arguably, that should be the most stressful in terms of cycles and torque applications.