What is ad frequency?

Frequency is the earliest reliable warning that a campaign is decaying. It rises before cost per lead does, which makes it the number to watch if you want to act before results suffer rather than after.

There's no universal ceiling, but on cold prospecting audiences performance commonly starts degrading somewhere between 2 and 4. Retargeting tolerates far more, because the audience already knows you.

Rising frequency with falling click-through rate is the textbook signature of ad fatigue. The fix is new creative, not a bigger budget — more spend against an exhausted audience simply buys more of the same impressions.