There isn't a magic number of executive hires where an annual search partnership suddenly becomes the right answer.
But if an organisation can already see three, four or five senior appointments coming over the next 12 months, I think it is worth comparing the economics and the operating model with buying each search separately.
Volume is only part of the decision.
Start with what you know is coming
Look at planned growth, retirements, succession risk, acquisitions, restructures and known leadership gaps.
Some organisations describe executive hiring as unpredictable when quite a lot of it is visible six or twelve months ahead.
If you know a divisional MD is retiring, two functions are being redesigned and an acquisition will need leadership, you already have a talent agenda even if the job requisitions don't exist yet.
Add the cost of separate searches
Work out what you would realistically spend commissioning those assignments individually.
Don't only compare headline fees. Include repeated briefing time, procurement, different supplier processes and the fact that each firm may have to rebuild market knowledge from scratch.
An annual model should offer commercial predictability, but cost saving shouldn't be the only reason to do it.
Is there useful work between vacancies?
This is the better test.
Could the partner be mapping succession markets, benchmarking pay, looking at future talent pools or helping assess internal options before roles become live?
If the answer is yes, an ongoing relationship can create value before a search starts.
If the only service you want is four unrelated searches, you may simply be buying a volume discount. That isn't particularly interesting.
Consider internal capability
A business with a strong in-house executive recruitment team may need very little external support even with relatively high volumes.
A smaller organisation might make only three senior appointments a year but have no internal research capability and get much more value from a standing partner.
So the threshold is partly about hires and partly about capability.
A sensible rule of thumb
At around three to five anticipated executive or senior leadership searches a year, I would at least model an annual partnership alongside traditional fees.
Then ask the more important question: would having an external talent team involved throughout the year improve the decisions around those hires?
If it would, ESaaS starts to become more than a different way of paying for search.