Like John says don't mess with it until it affects accuracy. I have seen a 1/3 MOA rifle get cleaned and shoot over 1 MOA until it has a few shots through it. Todd Hodnett (a trusted nstructor in long range shooting, also in Magpul's Art of the Precision Rifle) told me to think of the copper as a bearing in a car motor. It works the same. The copper not only cushions the bullet, but reduces wear on the barrel. It fills imperfections in the barrel and up until the point of causing flyers and then inaccuracy will help the rifles accuracy.
I usually get a couple hundred shots before I have to break out the Butch's bore shine in my usual range rifle. It varies for each rifle. Find out what round count your rifle performs best to, and clean.