I hear talk about people putting arsenals together, like "4 balls plus spare ball."
How many of us here use one ball during a game, strikes/spares regardless? I always figured that why waste money on a spare ball if I can make spares anyway? That gives me room for another "real" ball if I would need it.
What I normally do is whatever ball I start bowling a series with, I use it exclusively, be it middle-pin spares, sleepers, and right corners. If I happen to change strike balls at some point, I will most likely keep using the first ball I had for left/right corners. I ALWAYS use the strike ball/strike line to shoot spares in the middle of the lane and buckets/sleepers.