How many products does it remember, and for how long?

The list keeps up to the number set in Max products to show (default 8), and the browser cookie that stores the IDs is refreshed to a 30-day lifetime on every product view. The product currently being viewed is removed from the list, and the server-side lookup additionally caps the request to 20 IDs before loading them. Only valid, active products are returned, so deleted or disabled items drop out of the block automatically.