I worked for Jeollanam-do last year, and this year I am with EPIK in Jeollabuk-do.
My contract both last year and this year clearly state that it is mandatory to teach a summer and winter camp if your school chooses to, which can be up to two weeks. If it exceeds two weeks ask for extra pay. There are a lot of different contracts out there so review it. However, I was offered over a mil to do an extra week in the winter! Jeollanamdo is reliable and their orientations were awesome. Not saying I don't like EPIK, but I have a lot more trouble getting a vacation this year. Hope this helps! GO KIA TIGERS!