An experimental "configure expiration" command has been added. It currently allows specifying that factsets should (the longstanding default) or should not be candidates for expiration. See the documentation for further information and some caveats, and note that as an experimental command, it might be altered or removed in a future release.
Heston Hoffman Yeah, should have mentioned that – if you look at the "git log -p" and search (typically via '/') for PDB-4270, you should jump to the commit including the doc changes. I suspect the likely entry point would be the summary in documentation/api/command/v1/commands.markdown, i.e. the ### "configure expiration", version 1 (experimental) section.