Before adjusting the service plan for harsh road conditions, first judge whether the conditions apply using dust, temperature and road conditions, then assess the risk with filters, brakes and suspension checks and manufacturer requirements and local usage records. Adjust inspection intervals for dust, temperature, load and road conditions, but never go below the manufacturer's service requirements or promise longer intervals on your own.
There is no one-size-fits-all interval reduction for harsh conditions; any adjustment must follow the manufacturer's requirements and local usage records. Pair this with What should a buyer do if photos and final vehicle specifications do not match? on your first trial order. Supply and warranty responsibility for harsh-condition service must be written into the contract or service agreement; a supplier's verbal assurances are no substitute for a long-term commitment.