As to wood, I don't think we have ever had a broken staybolt on the WHEccles #3 Heisler, nor has it had any firebox work done on it. Likely it is original. It apparently did have coal burned into it during it's few years of operation in logging service in Idaho. Flues have gotten to weeping from time on the firebox end which is pretty easily remedied I think. Since this old girl has really gotten a work out year after year, I think this is a testament to wood being a more gentle fuel than coal or oil as far a boiler maint.