The sun
sun must burn 3.8x1026J/sec / 5.8x1014J/kg = 6.6x1011kg/sec.
The mass of the sun is 2x1030kg.
If the sun could burn all of its fuel, it should then be able to last 2x1030kg/6.6x1011kg/sec = 3x1018sec = 1011 years = 100 billion years.
Best theory says the sun will run out of fuel in its core after shining about 10 billion years.