It was just as "perpetual" as the AoC was.
Unity was assumed since all but the most idiotic realized that no state would be able to stand alone in a world filled with scheming European powers on three sides of the country. This is why no method for secession was even comptemplated at the convention. The Founders realized that seperation meant death and felt no need to discuss means of suicide. Thus, the word secession was never even mentioned in the convention if Madison, Hamilton or Yates are to be believed.
Read Jackson's attack on the Nullifiers he lays out the argument which devastates the argument for a right to secession.
His statement is a masterful display of simple logic and true history really though I realize that neither have no meaning to any who hope to rehabilitate the actions of the Slaveocracy.