A large inventory means a larger associated equipment handling , and there is no guarantee about the stock not giving more duds than qa cleared articles.
Didn't get you ? Are you saying QA is unsatisfactory or products have a limited shelf life . Long ago I happened to read an article on land based ICBMs in silos located inside mountains undergoing refurbishment to their propellants responsible for both - cold launch & thereafter. Can't recall if it was done at site or at the OEM .
Further given these were TN warheads , half life of certain fissile materials there meant it had to replaced with new ones. The entire environment in which they were kept was climate controlled .
Now granted these were strategic systems , hence the emphasis was on safety & efficacy of such systems more than costs but if the failure rate is high , there needs to be a Root Cause Analysis into it at the OEMs end & the user's end .
Let me also share with you another personal incident. Once upon a time one of our system providers who works exclusively with defence establishments got a sizable contract to install HVAC systems for a huge Naval Storage housing torpedoes & other sensitive electronic equipment. The project was initiated & managed by the MES. Now if you know a thing or two about this organisation it's a notoriously corrupt organization.
Most of the tech specs were diluted by our system provider once the tender was awarded to him , to cater to filling in the MES personnels's pockets who willingly signed on the deviations to the tender specifications. What do you think the condition of all those imported systems running into millions of USD will be when the balloon goes up. ?
Basically these are all high end complex systems and in aerospace industry we already have seen the very high rejection rate (hence the higher cost). This is basically why across the world armies that have limited budget also keep a limited inventory because consumption is quite low . It is always better to make the articles during use time than keeping a massive stock and then finding out half of that needing refurb.
If the reason lies elsewhere then it's time for our defence planners to become familiar with concepts in mfg like in the auto industry viz JIT aka Just in time pioneered by Toyota. Let me cite a recent example .
Apparently Solar Industry had recently released a statement in the media stating it had reduced the lead time to mfg a certain variant of the Pinaka rocket from some 60 days to 14 . The next step should be to bring it down to 5 & then to 2-3 if we're to cater to China.
You either identify the problem & work on it - Root Cause Analysis at the OEM or the End User & resort to storage of such systems in case of large orders or incase of systems or in certain cases where we can't , lean on the OEM to DRASTICALLY reduce lead time. Make it as a mandatory part of your developmental efforts AND one of the pre conditions in your orders for such items.