Earlier quoted context omitted.
True ( I didn't know! ), but is damn 30 years!! I'm not sure that they last so long, especially the gas-based. And I am getting an exempt, because I am using Holzpellets ( not sure how are they called in English ) EDIT: Wood pellets, that is.
I would be astonished to find any heating system more complicated than an open fire that lasted more than 30 years.
Wood stoves last basically indefinitely (i.e they are only taken out of service when the building owner decides they're sick of using wood) but you're probably gonna have to do something to make the seams seal better every several decades.
Fireplaces last as long as the masonry they're made from (~250yr and counting) as long as you don't let them fall apart and leak CO everywhere. I know some people who live in a house built in the 1700s and while they have forced hot air for "base load" they use the fireplaces to make the downstairs rooms extra warm almost daily in the winter. That said, this is only one step above your "open fire".