"We give no guarantees that the map will remain functional from one week to the next. We may reset the map as necessary."

To date it has not been necessary to reset the map, though there's been some discussions about how, when, and if we should reset. One of the primary goals of the snapshot server has been to allow people to try out the new features as soon as they're released. Resetting means any new blocks, structures, or terrain generation will be closer to spawn, but it also means that everyone starts from scratch which can make it more difficult to hop on chaos only occasionally check out new features.

As something of a compromise we'd like to try using MCA Selector to filter unused chunks based on InhabitedTime. After some test runs using the chaos map data 1 hour of InhabitedTime plus those within a 6 chunk radius gets most of the "builds" that are visible on the map, plus 2 * render distance around them. This will let people keep their semi-established bases, and their inventory so they can quickly get going with new content, but at the possible expense of some ... abrupt transitions between chunks.

To get rough idea of the density of chunks in the ~2000 blocks near spawn, here is PvE rev24 with the same filter applied, but the InhabitedTime requirement cranked up much higher to give a rough feel for what the selection would look like.

In this example, everything highlighted would be preserved and the surrounding chunks would be deleted so they could regenerate with whatever world generation changes may have been implemented.