It depends on the system. Gas boilers, warm-air units and radiant tube heaters need an annual gas safety inspection and burner service, which is a legal requirement. Heat pumps need an annual check of refrigerant levels, filters and electrical connections. Biomass boilers need the most attention: regular ash removal, fuel store management and annual flue sweeping.
Electric systems, including infrared heaters, panel heaters and storage heaters, need very little. There is no combustion, no flue and no moving parts in most cases. An occasional visual check and thermostat test is usually enough.
Budget for maintenance when comparing systems. A gas system that looks cheaper to run may cost more once you add the annual service contract.