Pipe is pipe, it has a useful life if it is constantly thermo-cycling. Think of the cast iron pipe they used to use for houses, shit gets used and degrades after so many years. Then do you have to pay the 30,000 for a re-drill?
I am curious to all these non-conventional concepts
I can see that...but how much thermo-cycling do you think is going on? I couldn't imagine it being more than a 5-10 degree difference since it attempts to keep a constant temperature and most likely isn't going through the amount of wear your hot water piping does when it's frequently going from ambient temps to having considerably hotter water pumped through them.
I'd want to believe the 25-50 year "life" is a conservative figure and they usually last closer to the 40-50 year range, but would like to hear more detail on the maintenance costs.
Either way, if it pays itself off 5-10 years, it wouldn't be anything more than a hassle and torn up lawn if it broke after 25.
My uncle has a couple wood-burning stoves in his old-as-hell farm-home they restored. They kept the original stoves, and either cuts some wood from his hunting land or gets some from someone that needs a tree cut. Puts out a good damn amount of heat.