Once all lessons are learned, a soul is considered an Ascended Master and can choose to stay in full communion with the Creator, joining energies, or they can choose to assist other souls or projects either by staying in the higher realms or reincarnating or both. It’s entirely up to them. If they commune and join energies with the Creator, this energy can help many worlds and entities in all parts of the universe, so however they choose to spend eternity is helpful. Thanks for the question. Blessings!