Earlier quoted context omitted.
I don't buy it. It's easier to make this argument for companies that are building their own hardware, since they know it can be immediately used. OpenAI's move is tantamount to hoarding for the sake of strangling competition. There was plenty of supply to allow for their plans without this move (especially since they will probably go bankrupt at this rate).
How exactly could they 'hoard' this? There's no place in the world to store that much undiced wafer. It will all go bad.
Nevertheless, unless you’re not storing them in a clean room of appropriate class (or in a vacuum pack), assume 18 months for undiced wafers.
In terms of size, I would think that stored in cassettes or carriers a vacuum sealed, it shouldn’t be too much. A 25 wafer pack is about half meter cube? A 40ft shipping container is about 68m^3. So one container can store about 140 packs of 25 wafers each. That’s 3500 wafers. They’re talking about 900k wafers. That’s about 260 containers. Call it 300 with extra space and stuff. Not exactly hard to provision.