Padding allocations is counter-productive
With just in time manufacturing it is counter-productive to pad or inflate item Lead Days and Job Days allocations because it distorts Time to Shipment targets for sell items and you lose the ability to track late POs and late starting jobs.
Allocations are inter-connected
Item allocations are inter-connected. Whenever an item has a To Order policy, its Lead Days and/or Job Days allocations contribute to the lead times of higher level items. So whenever you pad or inflate allocations at one level, it can inflate allocation values at the next higher level. Furthermore, the inflation effect magnifies at each higher level and can result in severely distorted Time to Shipment targets for top level items. This defeats one of the core purposes of Time to Shipment MRP, which is to achieve realistic and reliable ship dates.
Realistic PO due dates are important
P item Lead Days allocations establish PO due dates. If you pad or inflate Lead Days allocations, PO due dates are not realistic and you lose the valuable ability to track and expedite late POs in the PO Schedule.
Realistic job dates are important
M item Job Days allocations establish job start and finish dates. If you pad or inflate Job Days allocations, planned start dates are not meaningful and you lose the ability to track late starting jobs in the Release Jobs screen.
Meet don’t beat the schedule
To be successful with Time to Shipment MRP, make it your planning objective to meet, not beat the schedule. Strive for realistic Lead Days and Job Days allocations so that Time to Shipment targets are plausible and achievable and so that job and PO dates provide the feedback needed for staying on schedule so that orders get shipped on time.