MintUpdate APT cache retention without automatic purge

Linux Mint Software Manager and MintUpdate depend on APT metadata for package availability. The goal is to define a predictable cache retention policy that prevents stale package versions from appearing as pending updates.

The current configuration relies on the APT lists under /var/lib/apt/lists. MintUpdate triggers a metadata refresh on launch but does not purge obsolete entries from the cache. Linux Mint does not provide a built-in automatic cache cleanup beyond the standard APT clean operation, so outdated list files can persist across refreshes.

Behavior may vary between Mint 20.x, 21.x and newer releases, and the desired permission boundary for cache management is unclear. It is uncertain whether stale entries can be controlled via configuration or if manual intervention is the only supported approach.

Does MintUpdate expose a configurable cache TTL or purge policy for APT lists? Is there a supported configuration option to enforce automatic removal of obsolete metadata without manual cleanup? Under which version assumptions does the lack of automatic purge remain the documented behavior?