I have never checked the ring gap either, just always made sure that the cylinders were still in spec when fitting new pistons and rings. I have replaced just the rings when I know that I will be taking the pistons to the max mileage at the manx grand prix/classic tt to freshen up the motor between races. But otherwise, I just run the same top end for 300 miles ( both 4DP and 5KE) if doing short circuits.