Full transcript & breakdown
The test setup
Five accounts, identical creative, three ad sets each with 7-, 14-, and 30-day website-visitor windows. Budgets split evenly, four-week run, conversion optimisation held constant.
The 7-day window won on CTR in every account. It lost on total attributed revenue in four of five.
Why the short window loses money
A 7-day list is small and hot, so cost per thousand impressions climbs quickly and frequency saturates within days. The 14-day window kept CPM stable while still capturing purchase-intent recency, which is why it produced the best blended ROAS.
The 30-day window only outperformed in one account with a genuinely long consideration cycle. Match window to your actual median time-to-purchase rather than copying a template.
What to do with the finding
Start at 14 days, cap frequency around 3–4 per week, and rotate creative every two weeks. Re-test windows quarterly, because pricing and audience composition drift.
