The house I'm looking to buy has a 43-year old CGM-7 boiler. It works, although the flames are a bit yellow. My immediate instinct is to replace it before I move in, but I've seen conflicting opinions from "experts" in my reading so far. I'm posting here in the hopes that there is some sort of consensus.

Option 1 - Replace like for like with a new cast iron boiler.

The argument is that this is the cheapest upfront and uses the existing plumbing and vent/flue. It's simple, in a good way. There's no annual maintenance required, and I could even do some servicing myself. My concern here is that it's 2022 and it's not that smart to stick with old tech.

Option 2 - Upgrade to a high-efficiency condensing boiler.

Will cost more because the flue/vents need to be upgraded for pvc. I will get some floorspace back and lower monthly gas costs, although it will probably never pay for itself. I like this, because I care about the environment and floorspace, but I also hear that these things are more prone to breakage, and the annual maintenance removes a lot of the monthly gas usage savings. I could even upgrade to a combi boiler, although that is a debate in and of itself.

Option 3 - Just get it serviced and wait for it to break.

"These things last forever! The old stuff is built better." Why am I in such a hurry to replace it? This option kind of scares me, but I do get the logic.

Thank you for your opinions!