The only way to prolong oil and gas supplies is through efficiency. We have to use the 80:20 rule and focus on the areas that are the least efficienct in our lives - in my opinnion, these are cars and meat. The US has 200 million cars that consume 2/3rds of all of its oil. The US uses 25% of the world's oil, and so cars in the US alone use 16% of the world's oil [ref].
Personal vehicles require huge amounts of energy to get from point A to point B. A normal sized car has a 120hp (89.4kW) engine, which actually consumes more gasoline the slower the car is travelling, such as in city traffic, where average speeds are around 20mph with top speeds of 56mph (this is how the EPA tests city fuel efficiency at least). Using a 120hp engine is absolutely rediculous for this application. A recent study on althetes in the Tour de France shows that cyclists require only 246 watts to travel 20mph [ref], that's 360 times less energy than what is spent in a 120hp car to go the same average speed. A bike is the most efficient personal transportation device, 117% more efficient [ref] than simply walking. Of course, not everybody has a body that can generate 246 watts for a sustained period, so we must motorize bycicles, otherwise known as motorcycles, or better still, scooters. An electric scooter is the preferred way for getting from point A to point B in the city because it uses less energy than a car, but easier to sustain than a bike.
The second thing that we have to do is reduce our consumption of meat. Beef requires about 145 times more fossil fuel to grow than potatoes [ref]. David Pimentel of Cornell University calculates that it takes nearly twice as much fossil energy to produce a typical American diet than a pure vegetarian diet which works out to be an additional 150 gallons of fossil fuels per year for a meat-eater. So, the average American is using twice as much energy on a beef diet.
Finding a better way to get around in the city and reducing our intake of meat is the best thing we can do to prolong the oil and gas supplies. But, of course, running out of oil and gas is not the problem. The problem is in fact the environmental problems we will have if we use our oil and gas. The CO2 levels right now are at 370ppm. If we burn all of the oil that we know of, then CO2 levels will be 700ppm (by volume) [David Scott, International Journal of Hydrogen Research]. This is a huge problem. We have to stop using fossil fuels.