Wouldn't they start standing up stocklists for the AOP's as soon as the design is approved and building starts? Manufactures could give you information on normal wear rates and service items to use as a place to start your stocklist and projected needed stocklevels. Then add on normal items like bedding, PPE, replaceable electrical components (fuses, lightbulbs etc), machinary maintience items (zincs, filters, oils, impellers, etc) Then you start working on the more exotic items like specific valves, high wear pipe sections, spare glass and items unique to that design.