The impulse response functions are normally humpshaped—there is a small effect initially and the effect grows over time with the maximal impact occurring several quarters after the policy surprise. After the peak impact, the effect of the policy change on the real economy fades away, with the variables returning to their long run steady state values.
The benefits that accrue from the status of an international reserve currency have been demonstrated for decades by the United States. The US has not only received a steady stream of revenues from seignorage. They have also greatly benefited from the ability to finance large current account deficits over an extended period.