Yes you should clean your bowling balls after a certain amount of games bowled. Different bowlers have different number of games to when they clean their bowling ball. Some bowlers clean their bowling ball after 15 to 20 games. Some bowlers after more games then that or less games then that but I would say, you should clean your bowling balls after 20 games of play. You should be using a bowling ball clean that is made for cleaning bowling balls and you should be using a bowling towel to clean with. Below is the bowling ball cleaner that I use from amazon and keeping your bowling ball clean keeps your bowling ball rolling the right way and keeps the clean so it can roll the right way. Oil and dirt that the bowling ball picks up over time will decrease the ball hook and the ball will not work like it did when it was clean.
Bowling ball cleaner: Click here
Bowling ball towel: Click here