I have no idea what the actual figures would be but in my experience a good game shot fires their right barrel much more frequently than the left (I certainly do and I would not consider myself a particularly good shot!). If one assumes that this was also the case in the heyday of shooting at the turn of the century, a restorer like myself would expect to see a lot of guns with the right hand lock work 'shot out' or the jointing twisted. One doesn't so I think you can continue to shoot the right barrel more often than the left with impunity. Yes, there will be a wear imbalance but I doubt you will notice it in your life time!
