Here's my way of thinking when changing,..and I'm by no means the expert, but here's what I do most of the time..first, in league practice I try to start with the strongest ball I can, hopefully this gives me my best strike look. Since I hook the ball pretty good, with medium speed, I have to chase the "oil line" pretty quick. Usually (in league), on a typical house type shot, I can stay with the same ball for 3 games if I'm carrying. Sometimes in league I find that the pair is picking up more than usual carry down, and I'll change balls to move back to the right, rather than chase the oil, and get caught in the carry down, I may change from my Thing to my polished Vendetta Black. But usually in league I just keep moving inside with a strong ball, as long as the carry is good.
In tournaments, I start with a ball that will get me to the pocket the easiest, not necessarily my strongest ball, and give me a good entry angle. I want to start with a ball that will keep me out of trouble while changing pairs after each game. I find that starting with too agressive a ball in a long format usually won't let me use that ball very long and I have to change too soon. I like starting with some of my tamer balls until the lanes settle down, and open up a little, then I may go to a stronger ball. One of my favorites to start on the fresh in a tournament is my semi-polished Vendetta particle..as the track developes, and the backends hold a little more, I'll go to a Thing Returns, or a Thing once I know I can generate more area without the ball jumping all over the lane...On tough conditions I use a ball that will keep me out of trouble,..my Ven Black,Particle, and Crisis are all balls that are very smooth, and easy to read. In strike-fests I'll take the Thing Returns or the Anomaly.
I try and change balls with a reason in mind, usually to simplify my path to the pocket, and try and stay out of trouble and avoid opens.
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jimensminger D/T BallStaff