In terms of ac spares you miss the point that if a supplier has been allowed to let stock holdings dwindle to 0 based on historic uses and those items take 2-3 years to manufacture that is an expensive error.
Like I said above, this wasn't an error but deliberate policy promulgated by AMSO in the early 90s. Compounded by scrapping of War Reserves, which hitherto didn't count in the Max/Min levels. There was a huge increase in the number of equipments whose fit policy went from Full to Partial and Maintenance Policy to Repair by Cannibalisation. The Army, for example, were less than amused when the (admittedly quite ancient) comms kit specified for Apache had such a maintenance policy.
By the late 90s the routine paper exercises (e.g. ReGen) to check TTW capability would report high percentages of role limited aircraft, as they lacked basic equipment. The suppliers (by this time DLO, but same people) would say "Well, you haven't bought enough". The truth was the kit had been scrapped. Often, it had lain on the shelf unserviceable for too long, with no repair contracts (as the money had been wasted replacing other kit that had been scrapped). "The computer" thought it wasn't needed any more so the scrap order was given. AMSO had stopped knowledgeable human input at the same time he ordered the deliberate waste.
While the above are simple facts, you don't have to believe me. They were reported to PUS by both the Equipment Accounting Centre (1991) and MoD's own Director Internal Audit (1996). A 5 year gap, but the same RAF Chief Engineer (aka AMSO/AML). MoD's reaction to the 1996 report? "No further action" and destroyed in 2001 (info - FoI request).
The 1996 report was submitted to Lord Philip, PAC, HCDC and Ministers over the past 2 years. Which gets to the biggest problem. Given these bodies know the truth, why do they continue to protect those who are to blame, by not mentioning the report? It just encourages those who ask, as Fox 3 says;
1) How will this affect the career of the proposer, given current political priorities?
2) Will the proposer be long gone by the time any major snags show up?
3) Will it be politically unacceptable to admit the mistakes, and so necessary that they be covered up?