RRC rules say you can have 6 months off a residency if there are 2 completed years in another field. Some will do that - let you out at then end of December in your 3rd year (of 3 year residencies). However, as my PD said, "that's not what you're here for". Also, of note, you have to do it before your first day of residency - if you wait even that one day, you're in for the entire time.