Evidence Half-Life Ledger

Every research input an agency collects has a shelf life, and the shelf life differs by evidence type. A survey response about purchase intent decays in weeks because markets and competitor offers move. A behavioral observation from session recordings holds longer because it captures friction that rarely disappears on its own. A market-sizing figure from a paid intelligence source can stay usable for a quarter or more. The Evidence Half-Life Ledger is a simple register that tags each research artifact with its collection date, its evidence class, and a revalidation trigger. Agencies that keep this ledger stop recycling stale findings into new client decks, which is the quiet way retainers get questioned. The practical test: before any strategy recommendation ships, the delivery lead checks whether the underlying evidence is still inside its window. If it is not, the recommendation gets re-grounded or flagged as an assumption.