There is no right or wrong answer here. Whether you polish your brass or not is strictly up to you. How do you want your gun to look? If you like the "new" look, just keep your brass polished like it was when you bought it new. if, like most folks on this forum, you prefer the darker patina on your brass, don't polish it, just wipe it clean after you shoot it. The best patina is arrived at by just cleaning the crud off your brass but using no polish on it. This will give you a nice even patina over time.
Like I said, there is no right or wrong way to do it, it is all up to you and your personal tastes.