Teaching can be a pretty exhausting thing, especially ESL because you constantly have to grade your language to the level that you are teaching and having "conversations" about weather, hobbies, sports, house chores, schedules, etc can be mind-numbing. Although I teach mostly higher-level classes and can generally avoid those subjects, I still am "on-stage" for 15-20 hours/week, which can be tiring for someone like me who is naturally somewhat introverted. I submitted my grades a week ago, flew to Canada to visit the family and have been not thinking about work this entire week and I feel really good. Like last semester was this long-distant memory.
So, what I'm saying is this: even though you might be tempted to work the whole vacation if you teach at a Korean university because you can make a whole lot of extra money, it is usually not the best idea. It will leave you starting the new semester as less than full strength, and by the end of the often grueling 16 weeks, you will literally have nothing left. Money isn't everything and you need to think about your long-term mental health, especially if you plan on teaching at Korean unis for more than a year or two. Enjoy your amazing vacation time, even if you just have a staycation. When else in your life will you get so many weeks off?
How to Get a University Job in South Korea: The English Teaching Job of Your Dreams