Hi Rob,
I believe about 30 years should have been a reasonable life expectancy.
The engines have now been running for 140,000 hours and all the components & attached auxiliary equipment should normally be inspected every five years. Back in the old days (last century!!!), if I had been on here during a survey, I would have hit these castings with a hammer when they were stripped down. If they don't 'ring' right, you find out why. Maybe people are just to tired these days to 'hit & listen' to what the component is trying to tell you. Or, hitting it might break it, which then causes expenditure to replace the broken part.
Cheers
Skilly