I don't know about now of course, but during my time in the RAAF covering the Fifties and Sixties era it was common practice for pilots to simply swop seats if the co-pilot was given a take off or a landing. There was no automatic leg for leg then. It was purely a captain's prerogative if he decided to swop seats and let his co-pilot fly from the left seat. No special qualification or training was needed. The aircraft captain retained normal command responsibility for the duration of the flight. There was nothing about recency. The system worked well as far as I recall. In other words no big deal. Today it seems everything is a "big deal" in the eyes of the regulator.