Iteration: Any universe that the Abidan recognize as capable of sustaining human existence and living out a complete life-cycle.
Every Iteration has a destined progression. A world is born, it lives out its existence, and then it quietly dies, breaking into fragments. These fragments float through the void, crashing and combining randomly until they form into a new universe.
They are called "Iterations" because the thousands of universes currently in existence are thought to be different versions of the same original world or worlds, spun out in different combinations again and again for eternity. Even the Abidan Judges do not know when this cycle began.
On its own, an Iteration should exist for billions of years, except for a certain underlying requirement: each Iteration is anchored to the Way by sentient consciousness. As long as humans* are around, the world is tethered to the natural law and order of the Way. The fewer humans there are, the looser that connection becomes.
When humanity dies, the world dissolves.
*(The Abidan definition of "human" is pretty loose, but never too far removed from the humanity we know. When a new Iteration forms that may be able to support life, the Abidan select a new population of human pioneers and send them to inhabit a suitable planet.)