Frequency cap vs let-it-run — when capping helps and when it strangles

Frequency cap vs let-it-run — when capping helps and when it strangles
Frequency cap → protects against fatigue on retargeting and tight audiences, stops you burning the same 5k people. But on broad prospecting it chokes delivery and spikes CPMs for no reason.
Let-it-run → algo manages exposure on broad, fine while CTR holds, dangerous on small warm pools.
Rule: cap retargeting + small custom audiences (1-2 over X days). Never cap broad cold prospecting — you're handcuffing the auction.
Capping a 5M broad audience at frequency 1? You just paid premium CPMs to reach nobody twice.