The long run is a misleading guide to current affairs. In the long run we are all dead.
- John Maynard Keynes
Many modern economists, including fed chair Ben Bernanke, basically believe in the validity of Keynesian economics -- particularly the bit about the government intervening in the economy (through the federal reserve or debt spending) to mitigate perceived boom and bust cycles.
While in the long run you and I are clearly dead, our progeny are not. How good do you feel about mortgaging the economic future of our progeny? How good do you feel about it in the short run? I feel about as good about it as I do about stealing food from a baby.
So yes, we can quip a cute soundbite about the mortality of man, and use it to justify a flawed economic policy, bit is this really the sort of argument we want running our economy?