balancing your tires wont help them wear better-- if your tires are out of balance they will vibrate your seat(rear tires) or steering wheel(front tires). if they are out of balance they will cause patch wear, but if they are in balance then having them rebalaced wont make them last longer. When balancing a tire you are simply placing weight on the wheel were the heavyspot is in the tire and if done correctly the first time you shouldn't have to have them rebalanced unless u loose a weight.

 

don't you mean placing the weight opposite of the heavy spot?

If you ever have new tires installed, or have your existing tires swapped left/right, the balancing is part of the mounting procedure.