The most distinctive feature of the Buddhist planes is that every one of them ends. The texts assign lifespans to the heavens with actuarial relish, in figures that double as sermons: in Trayastrimsa a day lasts a hundred human years and the gods live a thousand such years; each higher heaven multiplies again, and the form-realm lifespans run to whole aeons. Yet the arithmetic always terminates. When a god's merit is exhausted, five signs appear, the tradition says: the garlands wither, the robes stain, sweat breaks out, the radiance dims, and the god no longer delights in the celestial seat. Then death comes, and rebirth follows karma, possibly far below. The canonical literature makes deliberate drama of the fall from Brahma's world: a being reborn at the summit through deep absorption, living so long that it forgets any origin, concludes it is the eternal creator, and the beings born after it agree, a Buddhist explanation for theism itself lodged inside the cosmology.
Two planes carry special footnotes. The Pure Abodes never host ordinary beings, only non-returners finishing the path, so they are the one neighborhood from which no one falls. And the plane of neither perception nor non-perception, the longest-lived of all, is treated as a trap: an existence so refined that practice is impossible there, an eighty-four-thousand-aeon parking of an unfinished journey. Permanence, the whole map insists, is not upstairs; it is out.