Then work on extending human lifespan. This is something the average HN contributor could be making progress towards. E.g. make a YC company working on capability advancement in biotech, or enabling technologies like atomically precise manufacturing.
7 billion years has got to be a bit of a stretch goal, even if you're very bullish on biotech...
Do we know of anything that has that type of lifespan outside of celestial bodies like planets?
Both the earth and sun are about ~4.5 billion years old. 7 billion is completely off the charts.
M type dwarfs can easily have a lifespan in the main sequence spanning many trillions of years with even their red giant phases estimated to outlasting even the main sequence of stars of our size.
A steller mass black hole's estimated lifespan would of course make even these seem like an eyeblink by comparison.