Ferric stearate, a three-tailed amphiphile, forms a bi-molecular layer on water surface. Molecules in the lower layer are in an 'asymmetric' configuration, Fe-containing heads touching water and three hydrocarbon tails in air, while molecules in the upper layer are in a 'symmetric' configuration, in pairs of 'Y and inverted Y' disposition of tails about the Fe-bearing head. Pressure relaxation at constant area (p - t curves) and area relaxation at constant pressure (A - t curves) of this bi-molecular layer can be modeled as a sum of three exponential decay terms with distinct time constants and weight factors. Relating the long-term decay with desorption of the total film thus indicates a remarkable long-term stability of the bi-molecular layer film. X-ray reflectivity study of the bi-molecular films deposited horizontally on Si(001) at various conditions of relaxation show no further growth along the vertical of any other layer. Under pressure relaxation molecules are transferred from the upper to the lower layer with a change from symmetric to asymmetric configuration, while under area relaxation the transfer is from the lower to the upper layer with a configurational change from symmetric to asymmetric.