2 Mar 2026 · 8 min
Creative fatigue as a leading indicator of CAC inflation
The CPA tile is a lagging reporter. Frequency, creative age, and contribution per new customer usually know first. User Acquisition Cost Analytics that ignores fatigue will scale a dying ad and call it discipline.
We met a travel team whose prospecting CPA had been “stable” for five weeks. Contribution margin on those new customers was not. Frequency on the winning TikTok had climbed past a point they had never written down. The ad was still cheap to click because it was familiar. It was no longer cheap to acquire someone who had not already been planning the trip.
Signals we actually chart
Average days since first delivery. Frequency within the geo you care about, not the platform’s global average. Thumb-stop or hold rate if you have it — optional, not sacred. And contribution margin on new-to-file orders inside your observed window. When margin falls while CPA sits still, fatigue is a leading suspect. Incrementality decay is another. You will not know which without a test, but you should stop scaling either way.
What fatigue is not
It is not a moral failure of the designer. It is not proof that “the algorithm changed.” It is inventory ageing in public. Treating it as a surprise every quarter is optional.
A pre-committed kill
Write the kill before the campaign launches: for example, “If frequency in Greater Bangkok exceeds X and new-to-file contribution drops Y% week-on-week, we cap spend regardless of CPA.” Pre-commitment keeps Monday meetings from becoming negotiations with a tile that still looks flattering.
Creative-to-Cost Mapping is the one-day seminar for teams who already know their join keys and want this chart operational. The flagship studio covers a shorter version in module six. See programmes or enquire.