What it is
A measurement problem disguised as a strategy debate.
The crossover is not a sharp line; the realistic range is three to twelve months, but six months is the working anchor.
The cusp is empirical, derived from longitudinal analysis of the IPA Effectiveness Databank by Les Binet and Peter Field. Rational/activation campaigns — the kind built around price, promotion, immediate offer, or task-stage capture — produce measurable sales response in the first six months and then taper. Emotional/brand campaigns — the kind built around fame, mental availability, and category-entry-point salience — produce limited sales response in the first six months but compound thereafter, and continue to widen the gap indefinitely beyond the cusp.
The cusp is a measurement problem disguised as a strategy debate. Any campaign evaluated on a window shorter than six months will systematically favour rational/activation work — and discriminate against brand work that is generating more long-run profit. When a prospect says “we tried brand and it didn’t work,” the first question is the measurement window. If the answer is under six months, the prospect did not measure brand performance; they measured a window where activation is structurally favoured.
Most SMB and mid-market reporting cadences are calibrated against month-end ROAS or quarterly revenue. Both windows sit below the cusp. The result is a near-universal pattern: brand investment is approved, gets measured before its effects exist, gets cut before the second half of its return arrives, and then gets blamed for not working. The measurement window, not the channel mix, is the load-bearing decision.