We just bought a house built in 1912 with radiator heat. During the major renovations phase we are considering a conversion to a different system. The system is drained and we have to test it to see if works. Is is worth keeping even if it does work?
There is much ado about efficiency today. The radiator system provides comfort. As long as repairs to the piping are not annoying, the system will last indefinitely. The radiator system is not a quick-acting system. The large amount of water and metal takes a while to heat up and cool down. This has been the attraction of the radiator system. Weather does not change rapidly either.
As long as the space taken up by the radiation is permissible, there is little incentive to change to a baseboard or radiant system if you are not trying to squeeze the last penny out of the fuel bill. The radiators send heat to your skin as well as other choices. A new efficient boiler brings the system close to the efficiency gained otherwise.
Just don’t put in a warm air system or you will notice the difference in comfort and noise.