[petercooper]

Everything is finite. It all depends on /how/ finite things are. Technological advances, increases in efficiency, and the influence of competing technologies (electric, hydrogen, liquid propane gas, and so forth) will all have a role to play.

It is typically very hard to accept that these things can have a big effect, but that doesn't mean they won't (nor, of course, that they must, but the odds are better that they will). The price of oil will be as "immaterial" within 50 years as the prices of horses or gas lamps were immaterial in 1940 compared to 1890.