Once rare and unique, our ex-PMs have proliferated at such a rate recently that it's becoming hard to keep up with them and their movements.

Kevin Rudd's in New York releasing another volume of memoirs. John Howard's on the ABC's 7.30 warning that the death of the Liberal Party has been greatly exaggerated.

Tony Abbott's supposedly open to returning as leader of the Coalition - though he will have to win his seat at the next federal election first. And Malcolm Turnbull is providing free advice to the government that deposed him - advice such as calling an early federal election so the state Coalition can be protected from the voters' baseball bats.

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Mr Abbott was roundly criticised for not following through on his promise not to snipe, wreck or undermine the government after he was dethroned - and justifiably so.

But Mr Turnbull has already shown his own worrying willingness to make life harder for new PM Scott Morrison and the Coalition by interjecting from the sidelines - whether on preselections, moving the Australian embassy in Israel or the national energy policy.

Mr Turnbull would say he has recent experience and political authority behind his advice, but so would every recent PM who couldn't help but make life difficult – whether deliberately or accidentally - for the person who replaced them.

As political history repeats, our ex-leaders would do well to look to Labor's Julia Gillard, who made good on her promise to leave politics if she was defeated by Mr Rudd and has mostly maintained a dignified silence since.

Though she was deeply unpopular with the public at the time of Mr Rudd's successful strike against her, it could be argued that Ms Gillard's conduct since has elevated her standing and history might just treat her more kindly than many would have thought at the time.

It can't be easy being an ex-PM, but it's not easy being a PM either. The least the deposed leader can do is give the new leader a chance to try to make it work - for the nation's sake, if not the party's.

Which brings us back to that collective noun.

Maybe a group of ex-prime ministers should be called an intervention. That does seem to have a bit of a ring to it.