It's logical to consider McCullum could miss the limited overs-only tour of Zimbabwe and South Africa in August in favour of getting heir apparent Kane Williamson more experience.
McCullum has been largely on the go since October. He played the majority of the New Zealand programme (with a small gap for the ODIs against Pakistan in the UAE), the World Cup, the Indian Premier League and will shortly embark on a seven-game stint with England T20 defending champions, the Birmingham Bears, which extends to July 22.
A special milestone also looms if he plays the three tests against Australia and two tests against Sri Lanka. Barring injury, the opening home test of what may be reduced to a two-match series against Australia would be his 100th in succession since his March 2004 debut against South Africa.
Of the 2791 test cricketers, McCullum is in line to be first to that mark. South Africa's AB de Villiers on 98 looked set to complete the feat against Bangladesh in Mirpur on July 30 but has opted to take paternity leave and miss the series. Only four players - Allan Border 153, Alastair Cook 112 not out, Mark Waugh 107 and Sunil Gavaskar 106 - have played more than 100 consecutive tests at any stage of their careers.
If McCullum retires from ODIs he will bow out as one of New Zealand's most inspirational and tactically astute captains, taking the national side to a World Cup final for the first time in March.
His winning record from 56 ODIs in charge (excluding three no results) is 58 per cent.
That rises to 62 per cent (28 from 45 completed matches) once he was officially handed the captaincy in late 2012. He is second to Glenn Turner (71 per cent - five wins from seven matches) and ahead of Daniel Vettori (55 per cent), Geoff Howarth (54 per cent), John Wright (52 per cent), Martin Crowe (49 per cent) and Stephen Fleming (48 per cent).
The series loss to England was New Zealand's first since October against South Africa. England revitalised their approach and made a quantum leap from a woeful World Cup.
The contests were compelling viewing, even if skewed in favour of bat rather than ball with a record 3151 runs scored for a series of five matches or less.
The cadence of Jonny Bairstow's 83 off 60 balls in the decider, after coming in at 40 for four in the seventh over, provided an apt denouement. Bairstow had been called into the side with less than 24 hours' notice.