pinnacle exception .. l don't lose balls often , but i am also not good enough to change balls every other round ... so i put about 7 to 8 that i use untill they get really scruffed out and affect the putting roll .. then i pass them to my buddies whenever they have a shot over water that they are not confident about ..
Titleist PRO V1's i have only the higher numbered pro v's 5-8, i keep a new dozen in there but have older PRO V's and some Nike ONE Platinums in there too, basically 20 balls in there
I only play Callaway Balls and I alway have 15 balls in my bag.
I use Precept Power Drive balls, or Strata Tour Straight balls. These are low compression, and I can hit them farther, and straighter than other balls.
I carry about 12 balls.
I usually carry about 18 balls. As for brand, I've been playing the Maxfli Noodle, but recently found a bunch of different balls, such as a Black Max, a couple of Pro V1s, a Solo, an AD 333, an NXT, and an NXT Tour. I've been experimenting with them, and think I'm going to change balls when I use up my current stock of Noodles. The Pro V1 and the Black Max are very nice, but I'm not planning to shell out the money for them regularly. I think I'll probably play the Solo for everyday golfing, and if I want to use a more expensive, three piece ball I'll play the NXT Tour.
Wilson Staff True Tour Elite's currently, but will change to the Tx4 or Px3 after this supply runs out. I usually have 6 or more balls in the bag and several dozen in the truck.