The Automation Promise
Google's pitch is compelling: "Let the algorithm do the work. More conversions, less effort."
And it's not entirely wrong. Performance Max can work brilliantly—for brands that actively manage it.
For everyone else, it's a slow leak.
What "Set and Forget" Actually Costs
The Branded Search Cannibalization
This is the biggest hidden cost. PMax automatically bids on branded terms, then claims those conversions.
Your branded ROAS looks phenomenal. Your overall efficiency quietly erodes.
We've seen accounts where 40-60% of PMax conversions were branded searches that would have converted anyway—often through free organic clicks.
The Audience Drift
Without negative audience signals, PMax finds the easiest conversions. Often that means:
- Existing customers (who'd buy anyway)
- Bottom-funnel bargain hunters (low-margin, low-LTV)
- Geographic pockets that convert but don't profit
Left unmanaged, your audience quality degrades month over month.
The Asset Erosion
PMax tests your creative assets automatically. Sounds good. Except:
- It optimises for clicks and conversions, not profit
- Winning assets often have nothing to do with your brand positioning
- Without refreshes, fatigue sets in invisibly
The Real Numbers
From our account restructure work over 2024-2025:
Average findings in "set and forget" PMax accounts:
- 35-50% branded search contamination
- 20-30% spend on products with sub-breakeven margins
- Asset groups unchanged for 6+ months
- No exclusion lists for existing customers
Typical recovery after restructure:
- 15-25% improvement in true new customer acquisition
- 20-40% reduction in wasted spend
- Stable or improved total conversions
What Active Management Looks Like
Weekly Tasks
- Search term review (limited but possible via insights)
- Asset performance review
- Audience signal adjustments
- Placement reviews (where visible)
Monthly Tasks
- Product segmentation by margin/performance
- Creative refresh planning
- Competitor landscape check
- LTV analysis on acquired customers
Quarterly Tasks
- Full account audit
- Structure assessment
- Target recalibration based on business data
The Real Cost Calculation
Most agencies charge management fees of 10-15% of spend. For a £50k/month account, that's £5-7.5k.
A neglected PMax account typically wastes 20-30% of spend on low-value conversions. On £50k, that's £10-15k/month.
Paying for proper management is cheaper than not paying for it.
The PMax Commercial Framework
We've developed a structured approach to PMax that maintains automation benefits while preventing drift:
- Commercial segmentation (products grouped by margin)
- Branded search isolation (separate campaigns for brand terms)
- Customer exclusion layers (stop paying to reacquire customers)
- Asset refresh calendars (prevent fatigue)
- Regular negative signal updates (prevent audience drift)
Concerned your PMax might be drifting? Our audit includes full PMax diagnostic—including branded search contamination analysis.