Depending on the ball, they last for about 90 to 120 shots; putts don't count. the most expensive balls don't last much longer, even if they have a bunch of durability dots. (players, including me, have tested this -- there's a chart somewhere in the forums).
For example, if I remember correctly, the WGT Tour SD has 1.5 dots and lasts for 110. The Callaways have 2.5 but last for only 120. THAT, if not theft, is VERY misleading.