Constant FRESH_DAYS 

pub const FRESH_DAYS: i64 = _; // 7i64

A content sealed in the folder longer ago than this and used again has its file made fresh (put), so that its writer, which may not have read the record using it again yet, never sweeps it from under that record (sweep keeps a file made fresh within UNUSED_DAYS). Half of UNUSED_DAYS: it must stay below it (it was 30 days, below 90).