Always keep something in your inventory.
My dad used to keep inventory for 3 - 6 months of production, in a non-IT related business line. Lots of people told him it was madness and such.
Disaster struck the local economy, specially the supply chain. The competition went nearly bankrupt, and we became the sole supplier of our product in 3 cities.
Hard drives don't depreciate in 3 months. Yes, you may think you are losing money (all that money stuck in the warehouse), but it is actually insurance.
And, for our main product, the raw material was perishable. You know, raw leather?. Hard drives have no perishable parts, afaik. Having some extra storage is essential, specially when your single supplier has only one facility for production.
You don't need to have 3 months in stock, but some amount that averts or mitigates disaster is wise.