[MilStdJunkie]

Yuuuuuup. This precise set of problems is why Systems Engineering was adopted in Aerospace and Defense, because maintenance plans need to know what the "loads" are for each replaceable (spareable) unit or assembly.

Today's SE has wandered far, far afield from original goals, tragically enough, but that was the original conception. One of the reasons for today's relatively toothless SE departments is the rise of finance into maintenance planning. Inventory depreciation is a cruel mistress, and "what gets spared" is rarely a SE judgement these days, at least in my experience. This has predictable results, but is partially offset by the exceptionally high bar for aerospace maintenance staff, who are generally pretty damn badass compared to, say, a washing machine repairman. Finance, naturally, would like to knock that bar down a few pegs, too.