If you look at the our American history, you will find that changes in party power happen much more frequently than it had in the first two centuries of the U.S. For many epochs of a decade or more, one party tended to hold sway in both houses of congress and the presidency, allowing much to get accomplished. Switches in party control of government usually followed rises in corruption/ineffectiveness that can happen to those who remain in power too long. In the last several decades, party control switches back and forth rapidly.