About fifteen years ago, a friend of mine, already a GP for 10 years, went back and did special (2-year) residencies first in OB/GYN, then in anesthesia.  He said the most important thing he learned in medical school the first time around was 

 "Medical school and residency was a brilliant example of planned obsolescence.  By the time they finished, much of what they learned was already out of date."

Love, Chanita, San Francisco