Statutory deadline clarification: conditional customs exemptions given a uniform end-date under amended notifications. Amendments insert an explanatory proviso into multiple customs notifications clarifying that specified conditional exemptions shall, unless varied or rescinded, remain valid only until the prescribed end-date under the statutory provision governing time limited conditional exemptions; one notification also omits several schedule entries and another adds the same clarification to a table entry, and the package includes an express commencement provision making the amendments operative from the stated enforcement date.