A single person with Immortality wouldn't cause that problem. Especially if they're a Scholar. They'd just get bored if they could even catch up absorbing all of the knowledge, depending on how limited your capacity would be, and move onto the next place and Culture. Once the current Planet had nothing to give they'd traverse the stars. You would already be used to isolation and loneliness, because everyone you cared about would be gone. There's not enough time in a day to do everything you could potential want to do, and new things are created everyday, so media is always progressing. New Books, Foods; assuming you need to eat, Movies, sights to see. If Health and Energy isn't an issue, you can just make your way there by walking, swimming, or climbing. Money may be an issue until you had a means to gain large amounts of wealth, but it's all hypothetical at this point, because Immortality isn't real.