There is a guy I know who works full-time as the Chef of a very busy restaurant and is the manager of a department in an extremely busy company that is wholly unrelated. He wants to retire by the time he is 55, but he works back-to-back. He leaves one job at midnight and then goes to work at the other job at 4AM. He doesn’t look tired, but he has to be. I tried working three jobs and lasted 6 weeks and before vacations when I was younger, I worked doubles for two weeks before leaving and got mono the first time and something else the second time and was basically in bed for a month. I finished last week working seven days straight. I am done.