The lead time to produce the co-products resulting from a base process is the same as the lead time for the base process. Cumulative Lead Time Roll-Up (13.12.14) copies the manufacturing lead time and the cumulative lead time for a base process to its co-products. Typically, the roll-up program is run for all items, not just those involved in co‑product/by-product structures.

By-product lead times are not derived from the base process, but from roll-ups of regular product structures and routings. Enter by-product lead times in Item Planning Maintenance (1.4.7) or Item-Site Planning Maintenance (1.4.17).