Peter Costello was often tagged the "lucky treasurer", having benefited from the mining boom and the wealth of revenue it brought to the budget.
Scott Morrison could also prove to be the luckiest treasurer in at least half a decade from the potential budget windfall a rebound in commodity prices brings.
But addressing a conference in Canberra on Tuesday, opposition finance spokesman Jim Chalmers said budget management wasn't about "carrying around rabbit feet and four-leaf clovers, hoping to get lucky".
The iron ore price has kept pace with Treasury's May forecast of $US55 per tonne, while coking coal has soared above $US200, more than double the prediction at budget time.
"These are certainly welcome developments, but budget repair shouldn't depend on luck ... governments need to make their own luck," Dr Chalmers told the 2016 ADC Canberra Connection conference.
Fiscal policy must suit the times and the budget must not be cut just for the sake of it when structural reforms were needed to get the books back into balance, he said.
Mr Costello, now chairman of the Future Fund, has asked the government to consider lowering the agency's target return.
The fund, introduced in 2006 by Mr Costello when he was treasurer to cover the unfunded superannuation liabilities of public servants, has a return target equal to the consumer price index plus 4.5 per cent.
The fund's managing director, David Neal, told a Senate hearing the request comes amid a low interest rate environment across the world and share markets being viewed as "fully valued".
Finance Minister Mathias Cormann and Mr Morrison are considering the request.
The fund now stands at just over $122 billion, more than double the original government contribution of $60.5 billion.
The government can draw down the fund from July 1, 2020.
It will have to decide by the next budget on its approach to drawdowns because it will be the first to reflect the 2020/21 financial year in the four-year forward estimates, Senator Cormann said.
The minister was less forthcoming when asked to give an up-to-date figure on the cost of policy decisions yet to be legislated, frustrating Labor senators.
Jenny McAllister wanted an update on the $18 billion figure cited in May's pre-election economic and fiscal outlook.
Senator Cormann took the question on notice, saying it changes all the time and he wanted to provide a proper, up-to-date list.
Labor senator Katy Gallagher found it hard to believe such basic information hadn't been prepared for the hearing or wasn't easily available.
