My experience (as an MS4)....three months after MS1, six weeks after MS2, and christmas and spring break (about 3-4 weeks total) during MS3 and then there is MS 4 (i've had 4 months!!). We also got christmas and spring breaks during the preclinical years, so it isn't too bad. I don't know what most people do...i've taken several vacations and worked here and there as well. Many people work/do research during the summer after first year, it just depends on the person and his/her goals. Good luck and enjoy your free time!