Constant RECENT_STAKE_TABLES_LIMIT 

pub const RECENT_STAKE_TABLES_LIMIT: u64 = 20; // 20u64

Number of recent per-epoch stake tables kept in memory.

reload_stake loads this many epochs from persistence on startup and prune_epochs evicts anything older as the tip advances, so a long-running node holds the same window as a freshly restarted one. Evicted epochs are recovered on demand via the membership coordinator’s catchup.