When CPA drifts up slowly over a quarter, the cause is rarely creative fatigue alone — pacing mechanics are an underrated culprit.
The three patterns
- Front-loading spend early in the month and starving the back half
- Auto-bid strategies re-learning every time budget changes
- Shared budgets across campaigns with very different conversion rates
The fix
Smooth budget changes, give bid strategies a stable learning window, and split shared budgets along conversion-rate lines, not just campaign theme.