We have a very old warm air heating system in our house (1970's) but it has been regularly maintained and the manufacturers assure me that spares will be available for as long as there is a demand for them. It therefore runs as if it were new and to be honest, apart from the extortionate price of gas, it suits us quite nicley. The whole house heats up quickly but stops as soon as the system is shut down, so when the weather warms up you are not left with hot radiators and all the windows open, which is my experience of radiators.
My gas fitter, who seems to be on some sort of sales commision incentive scheme, is forever pushing the cost benefits of radiators over warm air and wants me to pay out a large amount of money based on a very small 'theoretical' saving over the warm air system. I have worked it out that any saving would repay the cost of the installation of the new radiator type system in about ten years, by which time it would, apparently, need to be replaced? No contest in my opinion.