I'm probably the furthest thing from an expert in this field, being still a uni student and not knowing much about the industry until a few months ago before starting some research on it all.
But after reading all your comments I can see both sides of the story from an objective view. I think both sides have their fair points they are bringing across and in a way you are both right.
Creampuff, your argument seems to be that although there are these regulations saying you need to replace these components, in actual fact most of these components will last much longer than the manufacturers recommendation, and that the over-servicing of some areas, such as the injectors, can "potentially" introduce more problems than the it solves.
That is perfectly understandable and correct. But I think the point you are arguing about is yes this may be correct mechanically, but what yr right is trying to say is that is it really acceptable from a safety and liability point of view. Yes, a component may last 5 times its recommended replacement time 9 times out of 10. Yes 90% of vac pumps will last over 1000hrs. Yes injectors dont need inspection/cleaning as regularly with modern engines. But what happens when that 1 out of 10 times something fails? Who is responsible for the deaths that could occur from a failure mid flight? The manufacturer does not want that responsibility and it is there duty to ensure that does not occur.
That is why they appear to"over-maintain" certain areas, is to ensure that the 1 in 10 chance of failure does not occur. They do not want any failure rates, they do not want any accidents involving their aircraft and they do not want any lives lost due to a failure of a component they designed. Therefore their servicing intervals have a large factor of safety included to ensure the least liability towards them in the event a failure.
Yes this may increase costs at the expense of the consumer, but at the end of the day that is what they feel is necessary to ensure they have covered themselves from a mechanical failure. It is all a part of risk management, with a very conservative approach being taken. Replacement of parts may be completed much earlier than required but the risk of a failure is dramatically minimised than running the component close to the average failure time.
Running a component beyond its service life may be alright, it may not. There may be an issue, there may not. You may be over-servicing, you may not. It seems like a lot of the maintenance issues within the industry are based on maybes. Something may be able to operate for much longer than its replacement interval, but is it able to operate safely with the lowest possible chance of failure. And is running the risk that something "should" be alright to operate past its service life really an acceptable chance to take when you have other peoples lives in your hands? Fair enough if you are flying only yourself and you can take that chance with your own life, but can you really risk other peoples lives and take responsibility for that 1% chance that something might fail for operating past its service life?
With respect to the cleaning of injectors introducing more problems than it solves, it again is down to the manufacturer both taking responsibility for their designed aircraft, and also shedding responsibility as the component is now within their calculated acceptable factor of safety limits and the responsibility is now on the mechanic to ensure he takes responsibility for completing the work correctly without any issues. The inspection removes the liability of they "should" be alright. Cleaning the injectors every 500 hours means you know they were fully operational 500 hours ago, not they were fine last overhaul which is 2000 hours ago. There could be a 2% chance they could fail within 2000 hours compared to a 0.02% chance they could fail within 500 hours and these regular inspections remove the liability associated with the unknowns of when a component will actually fail from the manufacturer.
So after all that, I think the main thing im trying to get at is yes Creampuff you are 100% right in the fact that a lot of things can operate for much longer than specified, but someone needs to take responsibility for those few times that something fails early, and these early service intervals are the manufacturer taking responsibility to ensure there is no mechanical failure leading to potential accidents from there design and recommendation point.
Thats just how I see it anyway.