Why a Service-Line Breakdown Doesn’t Exist Yet
The natural next question after “how long does a typical agency engagement last” is whether that number changes by service line: does an SEO retainer outlast a branding project, does a PPC engagement run shorter than a full-service AOR relationship. No agency-benchmark-software vendor currently publishes that specific cut in a disclosed-methodology report this research could locate. Function Point, the vendor most likely to carry this data given its existing creative-agency benchmarking work, did not have it available at the URLs checked for this piece.
That gap does not mean the underlying question is unanswerable, only that the honest answer today is a narrower proxy rather than a full service-line table. The clearest available substitute measures a specific, common engagement type directly: the formal agency-of-record retainer relationship.
What the AOR Tenure Data Measures
The ANA and the 4A’s jointly track how long a client stays with its agency of record. Their most recent figure puts the current average AOR relationship at roughly 7 years, more than double the 3.2-year average measured in 2016. The same study found a specific lever that moves that number: clients without a mandatory, recurring review period stay with their agency 8.1 years on average, against just 3.8 years for clients who review the relationship frequently.
That is a real, meaningful engagement-length figure, but it describes one engagement type, a formal retainer relationship carrying the AOR designation, not the shorter project work, campaign-only contracts, or single-service engagements that make up a large share of what agencies sell. Presenting the AOR number as if it applied evenly across SEO, PPC, and branding work specifically would overstate what the underlying study measured.
The Numbers
8-figure-revenue agencies hold 92% annual client retention, against 78% for 7-figure agencies, a revenue-band cut of how long client relationships last once an agency scales.
Predictable Profits, 2025 Agency Growth Benchmark, as compiled by LoomDeck
Industry-wide account retention across major media-buying and planning holding companies fell to 21% in 2025, the lowest rate measured in eight years, a sharper churn signal than the AOR tenure figure above.
MediaPost, reporting on COMvergence’s Final 2025 Global New Business Barometer
62% of agency services are already sold as productized, fixed-scope offers, and 86% of agencies plan to increase productization, a structural shift toward defined-length engagements rather than open-ended retainers.
Sources
The external data in this article draws on the sources below. Figures described in the text as estimates or industry triangulations are directional and are not attributed to a single dataset.
- Predictable Profits, 2025 Agency Growth Benchmark, as compiled by LoomDeck
- MediaPost, reporting on COMvergence’s Final 2025 Global New Business Barometer
- RSW/US 2025 “Rolling Into 2026” survey, via shno.co