Billions of years ago, an extremely advanced civilization created an artificial world. Whether it is a ringworld, a shellworld, or something more isn't really relevant. This world's crust has a depth of a couple kilometers, but it does not have any resources other than soil and stone in it.
The original civilization moved its possessions to the world: houses, cars, ships, weapons, etc.
Due to the nature of this world, resource extraction is impossible (unless the resource is biological in origin). Mining is basically impossible.
Would it be possible for civilizations to recycle those materials for billions of years after the disappearance of the original civilization? Or would said materials disintegrate into nothing over time? How would an economy in this recycling world function?