Longevity of the RMH stove pipes

I have been reading a lot about the RMHs the last few days and have not seen anything on the longevity of the stovepipe embedded in the mass if the heater. I am an HVAC mechanic for commercial and industrial equipment and have found that the steam and moisture given off by such a highly efficient burn tends to rot out galvanized sheet metal very quickly. I was wondering how people are dealing with this or if is even an issue. About how long do these heaters last with heavy use before they need rebuilding?

Hi Jimmy; The pipe that we bury in the mass ,is carefully covered with cob so that when the hvac pipe rots out (it's expected to) , a smooth bore of cob will be there to replace it. How long does the hvac last ? I expect it varys from build to build, I would guess that within 5 years the pipe would start to disintegrate. The rest of the rmh should last a good long time depending on materials and quality of construction.