Wow, that elicited quite the discussion. I'm not sure if that is a good or a bad thing!
Thank you very much for the replies everyone. My apologies for rather selfishly swinging it back to my original query:
Is it fair to say that if a pilot, for whatever reason, can expect to be flying as commander from either seat station during the course of their duties, then they must swap seats every other OPC? It isn't sufficient to simply do an element of training from both seats.
And on the occasions that they do their OPC in "the other seat" (normally the left) it cannot be a combined OPC/LPC.
Is that about the measure of it?