Indeed, Friedman argued that the long and variable lags for monetary policy, due to outside lags, made monetary policy an unlikely instrument for short-run stabilization. Of course, some fiscal policy actions have very gradual effects as well – perhaps as gradual as those from monetary policy actions.
These slowing-acting policies include changes in capital gains tax rates, supply-side responses to changes in marginal tax rates, and many programs where spending builds gradually over time. Monetary and fiscal stimulus can complement each other when shocks are large and adverse and when interest rates are already low. However, putting together an appropriately stimulative fiscal package is not always easy.