Do not set a phased replacement rate by a universal rule. Track each unit in an asset register with identity, model, manufacture or acquisition information, repairs, faults, utilisation, and current condition.
Prioritise using repeat faults, repair and waiting cost, utilisation, operating impact, and spare-parts availability over the same period. Age alone should not decide retirement.
Derive annual replacement quantity from the budget ceiling, expected order or capacity need, supplier's written lead-time estimate, and a field compatibility check. Do not assume a fixed percentage or replacement year.
Document whether each retired unit will be sold, redeployed, repaired, or disposed of. Verify the replacement model against existing containers, accessories, washing, and storage flow in a pilot.
