For which scenario(s) should an advertiser consider optimization?

Optimization is a continuous process aimed at improving campaign performance. You should consider optimization when a line item is not meeting its desired KPI or goal, as adjustments are needed to bring it back on track. Similarly, if a line item is underspending its allocated budget, optimization can help identify and resolve issues preventing full budget utilization, ensuring maximum reach and impact. Even when a line item is achieving its performance goal, optimization is still valuable to identify opportunities for even greater efficiency or scale, pushing performance beyond current benchmarks. The only scenario where optimization might not be an immediate priority is if the line item is spending its budget at an optimal pace and already exceeding all performance goals, though even then, continuous improvement is often sought.