I'm guessing the coming spring session of the legislature will have its share of heated debate — debate over the Muskrat Falls hydro project in Labrador and the government's spending priorities in the budget.

But in the midst of this debate, how much concern will there be about a revenue source that has fuelled the province's unprecedented spending boom in the past half-dozen years or so?

Every time I look at one of those graphs showing projected oil production in the offshore, I'm struck by the fleeting opportunity that oil represents for the treasury, and by extension to the province's taxpayers. Oil has allowed us to pay lower taxes, to spend billions on infrastructure projects and to wipe billions off the debt.

But without new discoveries, and unless world prices go fantastically higher, we have seen the best of those halcyon days.

Oil production will level out for a couple of years, decline through 2016, and start to build again as Hebron comes online in late 2016 or early 2017.

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Premier Kathy Dunderdale has warned that government spending will need to be curbed. (CBC)

But this much is clear from those production graphs. Those years of production levels that exceeded 100 million barrels — 2002 through 2010, with the exception of 2009 — are over. We will get to 100 million for a year or two after 2017, but then production slides downward again.

Oil revenue has simply been a godsend to the province's politicians. It has eclipsed all other single forms of revenue in the provincial budget.

Last year, oil revenues — not including corporate income tax, and oil accounts for the lion's share of that, as well — were greater than the combined value of personal income tax, retail sales tax, gasoline tax, liquor tax and lottery revenue.

It's no wonder then that former auditor general John Noseworthy questioned the province's ability to sustain the new level of spending in the face of declining oil reserves.

And it explains, too, the premier's conditional promise in last fall's election to increase spending — conditional, that is, on the province's ability to pay.

None of this means that Newfoundland and Labrador, which triumphantly proclaimed the end of equalization payments more than three years ago, is about to slip back into systemic budget deficits.

But it is a warning. And as much as anything, that is likely to shape and shade debate over public spending for some time to come.