A sulfidation reaction model was built to estimate the durability of the deep desulfurization performance of zinc ferrite sorbent in a fixed bed reactor. The model is based on detailed change in sulfur capacity of zinc and iron during multiple desulfurization cycles in pressurized coal gas conditions. The model estimated the relation between the breakthrough time and the sulfur capacities of the sorbent. The relation between the breakthrough time of the sorbent bed and each sulfur capacity was estimated at various sulfur loads to the reactor, which indicated that the breakthrough time strongly depends on the change in zinc sulfur capacity. Extrapolation of experimental data for the initial 20 cycles of desulfurization suggested that zinc sulfur capacity might level off at around 40% of its initial value within 50 cycles. If the stabilization of zinc sulfur capacity is established, breakthrough time is maintained at around 70%, of that of fresh sorbent over more than 500 repetitions of multiple desulfurization cycles. It was also suggested that the verification of the stabilization effect require multiple cycle testing over more than 50 cycles.