Last-Time Buys: How to Size, Store, and Backstop an LTB
A product-discontinuance notice starts a countdown. The last-time buy is your one chance to secure factory-fresh inventory for the rest of a program’s life — here’s how to get it right.
The LTB decision window
When a manufacturer issues a PDN/PCN, it names a last-order date — often six to twelve months out. Everything after that date comes from inventory that already exists somewhere in the world. For long-life platforms in aerospace, defense, medical, and industrial markets, the LTB is frequently the cheapest insurance the program will ever buy.
Sizing the buy
- Start with honest demand. Annual build rate × remaining production years, plus service and repair demand for the support life — which often runs a decade past the last unit shipped.
- Add attrition. Assembly fallout, test rejects, and handling losses are real; build in a margin rather than discovering the shortfall in year seven.
- Respect the budget tension. Finance sees an LTB as cash converted into slow inventory. The counter-argument is the alternative: a redesign and re-qualification, or open-market buys at multiples of the original price. Put those numbers side by side.
Storing a decade of parts
An LTB only works if the parts are still good when you need them. That means ESD-safe handling, moisture control for MSD-rated devices (dry-pack with desiccant and humidity indicators, nitrogen storage for the long haul), stable temperature, and lot-level traceability so every reel can be tied back to the original factory buy. If your own warehouse isn't set up for that, third-party component warehousing is usually cheaper than the consequences.
When the LTB runs short anyway
Forecasts miss. Programs get extended, service demand surprises, a customer orders one more production run. When the LTB pool runs dry, the part is now obsolete and the franchise channel can't help — the remaining supply lives in OEM excess, distributor stock, and the global open market. That's exactly where counterfeit risk concentrates, so the sourcing discipline matters more than the sourcing speed: inspection on receipt, marking and construction verification against known-good references, and intelligence on suspect lots and suppliers.
Where RH Electronics fits
RH Electronics supports the whole LTB lifecycle: securing remaining factory stock before the last-order date, warehousing the buy under controlled conditions with full traceability, and — when the pool runs short years later — sourcing the obsolete part worldwide with every shipment inspected on receipt under an ISO 9001:2015 system, backed by ERAI membership since 1998 and GIDEP participation.