STEP 6
Last Time Buys & Stockpiling
Publishing Date: 05-Mar-2026
LTBs can prevent redesigns and ensure continuity—but they come with hidden costs. This step explores how to calculate LTB quantities, weigh redesign vs. stockpiling, and apply models like Porter Refresh and MOCA. Learn how to store, monitor, and preserve LTB inventory to avoid degradation, waste, and compliance risks.
Author: Prof. Dr. Peter Sandborn (Director, University of Maryland / CALCE)
Theme
Standard & Clause
LTB / Life of Need Buy Definition & Use
IEC 62402 §10.3 • SD-22 §4.4
Notification Handling (PCN, PDN, NRND)
IEC 62402 §9.2 • SD-22 §3.3
LTB Quantity Calculation & Service
Obligations
IEC 62402 §10.3 • SD-22 §4.4
Cost Analysis (NPV, Porter Model)
IEC 62402 §11.2 • SD-22 §4.4
Stockpiling & Storage Requirements
IEC 62402 §10.3; Annex C • SD-22 §4.4
Compliance Monitoring During Storage
IEC 62402 §4.1; §8.10 • SD-22 §4.3
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Prof. Dr. Peter
Sandborn
Position
Director, Professor
Company
University of Maryland (CALCE)
Peter Sandborn is a Professor in the CALCE Electronic Products and Systems Center at the University of Maryland. Dr. Sandborn’s group develops life-cycle cost models and business case support for long field life systems. This work includes obsolescence forecasting algorithms, strategic design refresh planning, lifetime buy quantity optimization, and maintenance planning. He is the author of over 200 technical publications and several books on electronic packaging and electronic systems cost analysis. He is a Fellow of the IEEE, ASME, and the PHM Society.
About the author
John Wombwell
John Wombwell, founder of CNX Technology and Innovation Group, has over 25 years of experience in Component Engineering and Obsolescence Management. A Royal Air Force veteran, his career spans work with radar, missile, and communication systems across defense, medical, and rail industries worldwide. Now focused on advancing proactive obsolescence management, John shares his expertise through CNX as initiator of the 12 Steps framework and the International Institute of Obsolescence Management.