I finished my Phd and re entered Med school in January. My third year rotations will be finished in January 2020. When should I begin prep for residency applications. In January or next summer for 2021 graduation?
This is correct for a 2021 graduation, but it really depends on your school. At my program you would be applying right now (during MS3, which would finish in December). We had 1 year of MS3 (January-December, which you are in now), and we only had 1 semester of MS4. So in your position, I applied right now and was on track to graduate for what would be spring 2020.
This kept our graduation times reasonable on an already long training pathway. I felt extremely well prepared for intern year (especially because the MS3-4 was all real clinicals, not part-time electives during MS4 a lot of people do).
If memory serves, 5 of my class of 14 finished in 7 years (including me), 7 in 8 years, and 1 in 9 years and 1 in 10 years due to this system, which is well below average graduation times (<8 years).
I would recommend this if your program signs off and you are prepared. It does mean scheduling SubI's during the middle of MS3 and "finishing" MS3 during MS4 with non-core electives (for instance, I had OB/GYN during MS4).