What about things that cannot be produced in a hurry? I am thinking of spares and consumables for important things.
A Just in Time approach to spares and support is not so good for things like major components for the electrical grid, medical life support systems, emergency service vehicles, and elements of our defence - such as ASW helicopters - mentioned repeatedly such as on the Carrier Strike thread.
I can see a situation in which the emergency services limit use of their vehicles during to a lack of spares.
There is no one-size fits all solution. Some things are lifed, and you can only hold them for so long before they have to be replaced. That’s fine if it’s a set of O-rings for the gearbox of a helicopter type, and you only have 20 of them. But if it’s medical masks for your health service and you need hundreds of millions of them, then perhaps that’s no so affordable to keep that many on hand.
Sone things just become obsolescent. Take the BURLINGTON bunker, for example. It was pretty much obsolete the day the Russians acquired hydrogen bombs. It persevered, however for about 40 years beyond that. Look at the technology though. Manually-switched telephone exchange. It’ll survive an EMP pulse, but you can’t connect it to anything else today. It’s like trying to put an audio cassette into an MP3 player. No computers. Typewriters aplenty, but there’d be no skills to use them, woefully inefficient, and no means to distribute whatever’s been typed outside the bunker. Let’s say they installed computers. They have to be maintained. They have to be swapped out every so often in a technology refresh. You can’t be using 386-based computers running Windows 3.11 in an IP-based world. Who would hold the budget to refresh them? What an easy line-item to delete too, if there’s budget pressure (When isn’t there budget pressure?). “Hoskins, when was the last time we used BURLINGTON?”. “About 8 years ago, Minister”. “Right, strike the new computers for this year”. “Again, Minister?”
From the 1950s through the 2000s, the government maintained a fleet of 1000 basic fire trucks at Marchington. Except a) they were really just pumps, b) the crews (Auxiliary Fire Service) were disbanded before I was born, and I’m 52, c) they were only used on two or three occasions, nationally. There was the incongruity of having these ancient, barely-capable machines being used by barely-competent hastily trained squaddies, while tens of millions of pounds’ worth of firefighting equipment sat idle, due to some equally ancient labour relations ideas that meant they couldn’t be retrieved from the stations. I’ve no doubt their existence fostered a false sense of security too, on the part of some governments. Really, they were intended as auxiliary pumps to get water into cities, not really to fight fires, and certainly not to deal with RTAs.
Yes, you can have too much resilience.