Maintenance is the line that explodes when ignored. Budget preventive maintenance per machine, plus a breakdown allowance.
Tyres (per 1,000 hours), ground engaging tools, crusher liners (per tonne crushed), screen panels, conveyor belts, bearings, hydraulic hoses, welding consumables.
Budget 8–12 % of capex per year for preventive; add 20–30 % uplift if maintenance is reactive only.
Rule of thumb: 8–12 % of fleet capex per year for an open-pit operation; 12–18 % for crushing-and-screening plant.