How long would 100 earth masses' worth of hydrogen last a billion people?

Update: At the end of the stelliferous era, some people settle a rocky rouge planet orbiting a Saturn-like gas giant. The gas giant contains 6e26 kilograms of hydrogen. The settlers begin using hydrogen harvested from it as fuel in fusion reactors. The atoms-to-consumers efficiency is 50%. Their population grows to one... show more At the end of the stelliferous era, some people settle a rocky rouge planet orbiting a Saturn-like gas giant.

The gas giant contains 6e26 kilograms of hydrogen. The settlers begin using hydrogen harvested from it as fuel in fusion reactors. The atoms-to-consumers efficiency is 50%.

Their population grows to one billion, but by agreement they hold it there. Each settler is allowed to use 500 kWh of energy per 24-hour period.

How long will it be until the gas giant is all used up?
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