You wil I'm sure be aware that component lives are given a notional life extension of 10% to allow for the scheduling of maintenance in line with operational requirements. It was envisaged that one would plan to have the component changed as close to the published life as possible and in the UK I believe we were required to base our planning on that strategy.
In other parts of the globe it is common practice to base the DOCs of the component lives plus the 10%. These operators PLANNED to use the life extension as a matter of course.
Now compare that with a military philosophy of keeping the hardware in tip top condition. Why do the military behave this way? Because they know darn well that when the bullets start to fly the maintenance schedule goes out the window and you do what you can when you can and it pays to be ahead of he game when the war starts.
The commercial world is another kind of war but the enemy is Chapter 11. If you can't pay the bills you go down. Those that play the game are those the have been around the longest and have learned the hard way not to cut corners or waste money. They are also aware of the false econmoy associated with cutting corners on maintenance but I doubt that even these guys would be changing a component early because it was looking a bit worn. They might run a surveillance programme on it but if it is going to last the course then they will make it last the course. To be sure to do that you need engineers that know what they are doing - that's another story. Maybe HUMS can be a useful tool in that quality engineer's toolbox but as you say, it's not the be all and end all.
A few years ago I was auditing in the Americas and found a pair of engineers dismembering a C20 (splitting the modules) on a grubby hangar floor. No approvals and no special tools. A Chief engineer had just been disciplined for splitting a pair of u/s 332L1 MGBs and swapping gearwheels in order to make one serviceable unit. Once again no approvals and no special tools. This is what we are up against. Why? Well in my opinion out of sight out of mind. If the person authorising the use of a machine to carry his employees to and fro actually had to fly his wife and kids in them once a week to prove his faith in the choice he has made then maybe things would be different and he would pay the going rate for a PROPER service.
Grrrrrrr.
G.
