I wrote the bulk of the previous post before (re-)reading a Robert Solow essay that I'd largely forgotten about, Sustainability: An Economist's Perspective.
Please do yourself a favour and read it. It's a great piece of writing that is not only concise, but remarkably prescient and even funny. More importantly, Solow essentially makes all of the points that I tried to convey in a far superior manner. I'm pleased to say that he even mentions the Hartwick Rule and compares Norway's management of its oil wealth to that of its less prudent North Sea neighbour, Britain.
For what it's worth, if you're interested you can see my basic take on Thatcher, as well as Blair and co's, spendthrift approach to the UK's North Sea oil resources here. You'll also get the chance to see a reactionary libertarian response for free![*]
[*] Freeman, if you're reading this, just kidding bud. Although...