You might want to get a spare ball.
Balls don't last forever, so you shouldn't use the strike balls for sparing, unless there's many pins left.
Some people use the strike balls when there's pins on the left side though, but not when there's pins on the right. For right handers.
I'll stick with my plastic ball for sparing from now on though. Whenever I try using the strike balls, I mess up, not always, but often.
The strike balls is good to use if you got a split. Not on baby split though.
Last week at practice I had a split of 3-6-7-10. Used my Jackal and got it to hit in between 3 and 6 and got them all down. Was pretty cool.
Was the second such split that practice, didn't get the first one down, but was close.
If you mostly play on heavy oil like we do here, then you could of course get a ball that's meant for light oil and use it as a spare ball. It could be good to have a ball that will slightly hook when you have the 10 left, in case you get it too far out and then it'll hook before going into the gutter, maybe.
Tore Torgersen told me that he didn't want to sell me the Motiv Arctic Sniper as a spare ball, because it hooks a bit. But Motiv says it has 0 hook potential.
Ascent might be good light oil balls to use as spare ball on heavy oil.