In the olden days you didn't get to be boss of a major company, government department - or this newspaper - until you were in your late 50s or early 60s. You stayed in the job until you reached what was then imagined to be the official retirement age of 65. So whether they performed well or badly, no one spent all that long in a top job.
(Going not that far further back, you didn't get to be governor of NSW, Anglican archbishop of Sydney or editor of the Herald unless you were an Englishman, recruited from the Old Country. Having done your bit in governing the colonies, you retired to the Home Counties.)
These days, top jobs go to much younger people, which means they get a longer go at it - assuming they work out - but have to give it up and let someone else have a turn well before they're old enough to retire.
Dr Ken Henry was 43 when he became secretary to the Treasury in 2001. His five-year term was renewed in 2006, so he's held the job for almost a decade and now it's time to move on. He's likely to take a long break before accepting another job.
Henry is what his present political masters aren't: a believer. Like all his predecessors - and his successor, Dr Martin Parkinson - he's an economic rationalist. He believes in the power of market forces and the need to ensure they're harnessed to advancing the wellbeing of the community. Sometimes they need to be let off the leash, sometimes they need to be channelled, sometimes they need to be introduced to an area where they haven't existed but can be used to improve its performance (though sometimes this is a bad idea).
At a time when our politicians seem bereft of bedrock beliefs and values, and most government departments seem to have lost their compass, it's good to have a central agency with a clear view of what constitutes good policy in the public interest and an unwavering willingness to argue for it.
Henry continued to inculcate the Treasury View among his troops - maintaining their esprit de corps - and within the government.
Parkinson is a macro-economist, but Treasury is no longer involved in the day-to-day management of the macro economy - except to the extent that its secretary is an ex officio member of the outfit that does manage the economy, the Reserve Bank board.
Henry is a micro-economist, and Treasury has more than enough to do urging governments to take a rational approach in all the many markets it has influence over. And nowhere is that need greater than in using "economic instruments" - such as a price on carbon and the trading of water rights - to reconcile the conflict between economic activity and preserving the natural environment.
Henry is an environmentalist (as well as an active defender of kangaroos and wombats). He played an important part in developing the Howard government's plans for an emissions trading scheme, as did Parkinson, and Treasury modelling informed the Rudd government's initial attempt to get a scheme up.
There was a joke that the people running Treasury were greener than those running the Environment Department.
Parko, originally Henry's deputy in Treasury, left to work on trading schemes, taking various senior people with him and eventually being appointed to head the new Department of Climate Change.
Now he'll be succeeded by another Treasury man, Blair Comley. So under Henry, Treasury managed to colonise the environmental departments.
Is Henry "one of the greatest of all Treasury secretaries" as Julia Gillard has said? No doubt. Is he the greatest? He's the greatest in my memory.
Treasury was at its most influential during the term of the Hawke government, but I give the credit for that to our greatest ever treasurer, Paul Keating, a man with a deep understanding of how to obtain and use political power, and who needed a purpose to fight for. Treasury supplied that purpose, affecting his conversion to economic rationalism.
Treasury's highest institutional objective has long been to dominate the economic advice going to the government, and no secretary has been more successful in this than Henry, thanks to the arrival of the deeply insecure Rudd government, which sought to hide behind the authority of the supposedly independent Treasury.
Henry obliged - after all, Treasury is not and never could be independent - and became a key adviser to the prime minister, as well as being appointed to every policy committee worth being on.
That was Treasury's institutional reward, the rent it received for the use of its authority. Henry's personal reward was being allowed to head his own comprehensive review of the federal and state tax system.
Those who condemn the government's cursory dismissal of the Henry report have missed the point. Henry's ambition was to lay out a blueprint for long-term tax reform, which would provide a guide to his Treasury successors and an antidote to political ad-hockery for decades to come.
Tax reform was Henry's first love and he played an important part in all the reforms of the past 25 years. He was the first Treasury secretary to acknowledge the validity and usefulness of behavioural economics.
His tax report would have been better had he made more use of behavioural precepts.
Despite its loss of day-to-day macro management, Treasury - and budgetary policy - comes into its own when recession threatens. Here the micro-economist excelled himself.
He played a central role in the Rudd government's response to the global financial crisis and, learning from the policy errors in the severe recession of the early 1990s, urged Rudd to "go hard, go early, go households".
Most punters will never know it, but many owe their continued employment to that wise advice.
