The planet of the Non-Eternals is just like the Earth, a filter of consciousness. The difference is that they have already reached the Golden Age, and live in a Paradisiacal society. But people there are born, have children, and die, just like on Earth. They live 10 times longer than us from what I understood.
They are also entitled to eternal life if they have a positive life. Every year, there are contests, and the best person of each province is selected. These contestants are on probation for 3 lifetimes. After those 3 lifetimes, the winner will be allowed to join the Eternals on the Planet of the Eternals.