What is long lead time planning?

Long lead time planning is the practice of building a Supply Chain plan when the replenishment lead time is long enough that the order has to be committed well before demand is knowable, typically anything beyond about three months and commonly four to six months for goods produced in Asia and shipped by sea.

It is a distinct discipline rather than ordinary replenishment with bigger numbers, because three things change at once. The forecast covering the order horizon is much less reliable, so the decision carries more risk. The order quantity is usually dictated by a shipping or supplier constraint rather than by the net requirement, so the plan cannot simply order what it needs. And a large share of total inventory sits in transit rather than in the warehouse, so any plan that reasons only about stock on hand is missing months of coverage.

Practically, it means planning against a range of demand outcomes rather than a single forecast, modelling the constraints that set order size, and treating in-transit stock as inventory.