If one had a large-scale home retrofit program with the goal of saving energy, what would be the pros and cons of a policy to replace all standing pilot light furnaces? Health and safety improvements count, as do energy savings.
1) Turn down the gas pressure, that is a crazy big pilot
2) Replacing this cast iron beauty is a lot more complicated than it sounds. Unless the distribution system is also updated, return water temps will be >120F resulting in your new 90%+ mod con boiler running at 80% efficiency. A boiler like this if running properly will be 75% efficient.
3) The coal soot left in every possible place throughout the distribution system will plug up the low flow heat exchanger of any 90%+ boiler I have seen except the Burnham Revolution. I learned this the hard way!
4) Most people do not have the funds for boiler replacement and serious weatherization upgrades. When forced to choose, I will recommend the weatherization every time.
5) In 50 years when this boiler is still running without issues, how many times will the tech have to come out and service the mod con that is now past it's useful life? If you follow the manufacturer's advice, 16 cleanings at $100 each adds $1600 to the cost of operation.
Most HVAC contractors make their money with changing these old dogs out, but they still have their place. By reducing the load, through air sealing and insulating we reduce the fuel used and if after that the homeowner still wants to buy a Prius or solar panels or a new mod con boiler, then great, but not until the enclosure is tight.