A maintenance contract is not really a service you are buying. It is a bet that finding a worn rope on a Tuesday morning is cheaper than finding it when the crane stops mid-lift on a Thursday afternoon.
That bet only pays if the contract is written to find things. Plenty are written instead to schedule visits — which is not the same, and reads almost identically until the first breakdown.
These are the questions worth putting to any supplier, ours included, before signing one.