I’m kind of with your agent on this. My house in PA had a heater put in in 1957 (before I was born) – it still worked. It was an oil heater so I bought a maintenance contract for it from my oil supplier. They replaced the blower, burner, and some other thing in the 8 years I owned the place. It was still running when I sold it.
Our current house had the original heater until 2008. The house was built in 1964.
Just cause it’s old doesn’t mean it’s going to fail in the next couple of years. It could, but it’s not necessarily going to.