Since the time of oil extraction started, the known amount of extractable oil, for the current consumption at that time, has been at 40yrs. You can find articles in the late 1800u2019s, early 1900u2019s, 1950u2019s, 60u2019s, 70u2019s, all the way up into the 90u2019s at least that show weu2019ll run out of oil in 40yrs. Today though weu2019re at about 70yrs for current production rate with known reserves.The fact is we always had newer technologies to find and extract it. Weu2019re coming to an age where weu2019re within decades of not needing oil for the vast majority of fuel purposes (probably will still need it for air travel), weu2019ll need it for production of various materials as well.Coal the world as a whole has identified about 1.3Trillion Short Tons of Coal, we consume about 9B Short Tons of Coal a year, thatu2019s about 144yrs worth at current consumption. Coal consumption has been leveling off, and is expected to start dropping.Natural Gas proven reserves 187,300,000,000,000 m^2 consumption 3,468,600,000,000 per year - 54yrsSo, if we continue using like we are, weu2019re probably could sustain it at least 100yrs maybe more, one could assume we can identify and locate more fossil fuel resources as we have always been able to do so. But more importantly, we are likely to be vastly reducing our reliance on fossil fuels in the decades to come, Weu2019ll never likely run out of coal as weu2019ll stop using it, oil - our reliance should be drastically reduced. Natural gas, maybe the one thatu2019s most likely to be closest to being depleted, but still not likely before the year 2100 IMO.