If you're a numbers man, that sounds like a good time to step away.
He will be at the world T20 tournament in India early next year, and after that, McCullum's cricket activities may largely be confined to the various T20 leagues around the globe, although that was not put in those words yesterday.
"We've had a very good past 18 months but we've got some real challenges ahead of us and we need to keep making progress," McCullum said.
"This is a young, emerging side with some very big series on the horizon and it's a really exciting time to be involved."
Although in his case, not for much longer. At 33, the body and perhaps the spirit may feel it has done its dash on the international stage.
His time, after a bumpy introductory few months, has coincided with the emergence of an exciting New Zealand team playing heady, spirited cricket.
Actually it's no coincidence.
McCullum has a team playing in his image, enjoying themselves and becoming a major force in the game, albeit still needing a bit of refinement around settling for a save rather than a too-bold attitude when the time is not right.
The question will soon become how well they will carry on his legacy after he has gone.
McCullum's heir apparent, Kane Williamson, is a different personality. He's a terrific cricketer, destined to become New Zealand's best batsman, and is currently seventh on the world test rankings and sixth for ODIs.
But will Williamson park up three slips and a gully midway through an ODI innings as McCullum has been wont to do? Not so sure about that, and in any case Williamson - assuming it is to be him taking over - will want to do things his way.
It's easy to forget there have been times when McCullum's instinctive attack-at-all-costs strategy has not worked. But you remember the moments a punt came off.
McCullum can now set his sights on tackling the Australians. A series win in Australia out of reach? No, but it'll take some getting. The challenge is sure to appeal to McCullum.
Once the Aussies are out of the way, and the world T20, McCullum will have had three and a half years of jam-packed activity as leader. That will probably be it.
Then it'll be the Brisbane Heat - for whom he has signed a three-year deal to play under his old teammate Dan Vettori - plus Indian Premier League and perhaps English and Caribbean T20 commitments.
When he walks away McCullum can be content that he has been among the most influential leaders New Zealand sport has had.
