The stone stoves, such as Hearthstone, appear to carry relatively small slabs of soapstone, or granite. Yet, one hears that they appreciably prolong the heat radiation. I already bought an all iron woodstove, rather than a soapstone/granite one, because I wanted the quicker heat-up & cool-down through most of the heating season. BUT, would it be worth the $30 per Sq Ft cost of placing a temporary (removable) slab of granite on top of the stove and a couple larger movable slabs beside it during the all-day long log consuming weather, so as to maximize my heat mass, and minimize the wood consumption? Would the effect be negligible, or sizeable? What's your guess?