Q:

Use years / Years of Use?

I am writing a paper about pipelines in Seoul..
And I have a grammatical problem to describe pipeline's years of use... 
I'd like to describe the time passed since they were installed. 
Which one is correct and natural? 
'Use years of pipelines in Seoul,Korea' 
'Years of use of pipelines in Seoul,Korea' 
'Pipelines' use years in Seoul,Korea' 

A:

Use years… or Years of use… or Pipelines' use years… look like titles, not parts of the report. If those are the given choices, my vote would go to Years of use of pipelines… but in real life I’d expect Life expectancy of… or something like Planned and achieved years of use…
Are these pipelines planned or payed for in man years, calendar years or how, please? Train operators use track miles, route miles, passenger miles and other equally different measures of the same line on a map even before they take time into account but the grammar shouldn’t change.
Here, if the pipe is replaced or painted, the maintenance guys will presumably be interested in the life expectancy of the parts, not the whole pipe-line, and measure that in something like pipe-years or paint-years, not pipe-line years.

