I have a sim with a mixology certification and 2 degrees. He never had to quit his job while going to college. Sometimes I leave work early, go to work late, or use a vacation day. It's manageable; you don't have to quit. If you have 5 vacation days, that covers a whole semester right there, though you don't even need 5.
One of my sims is switching from an astronaut to a teacher, so that's why I got him a second degree in education. Another sim is just an egg head and wanted to learn robotics on the side so I got degrees to complement that. They look nice in the sim panel, lol.
