Thomas Jefferson believed the constitution should be a living document.
"let us provide in our constitution for its revision at stated periods. What these periods should be, nature herself indicates"
Nature itself dictates so through the length of a generation: If the constitution outlives human, we end up being ruled by the dead rather than by the living, as a democracy presupposes.
One could assume this would mean that they should last a lifetime, but in a letter to James Madison, Jefferson expresses the belief that each generation have the right to their own:
Every constitution then, and every law, naturally expires at the end of 19 years. If it be enforced longer, it is an act of force, and not of right
This was the ideas of a central founding father of American democracy. Yet today, authoritarian tools in the supreme court are using their perceived legislative intent of the founding fatgers to justify all kinds of fucked up shit. The intent of the founding fathers was that the nation should move the fuck on and not be stuck in the past.