The million dollar question I get a few times a day.  And the answer is..........."I dont know".  

Due to the number of variables in play, it is impossible to tell you how many swings your bat will last, however, there are a few key points of reference that will give you a directional idea.  Keep in mind even with the answers to the questions below, it is still impossible to tell you the number of swings, but it does give a better idea if it will hold up more so vs not

1) How hard do you hit he ball?  this is a pretty simple one...........harder you swing, the faster your bat will break.  

2) How do you hit the ball?  If you tend to hit the ball flush (dead center on the ball), this type of impact will break a bat faster than if you got good spin and consistently hit the bottom half or third of the ball.   You may hear people talk about back spin or lift.  This is essentially how it is done

3) Temperature.  Colder the temp, the faster your bat will crack.  Composite bats flex.  In the cold, composite bats harden up and do not flex at impact.  This is a recipe for disaster.  It is my recommendation to keep the temperature above 65 degrees Fahrenheit.  Most manufacturers, if you were to read the warranty policy, also suggests a similar temperature

4) What balls do you use?  Case in point, harder the ball, faster your bat will break.  Yes harder balls are more fun to hit, but they are also fun balls to snap a bat in a few swings.  My suggestion is to limit the balls you hit to the ball that was approved for the bat you purchased

5) If you purchased a shaved bat, how heavy was the shave?  Heavier the shave, faster the bat will break.  

6) How much end load is in your bat?  If you were to take a super slo-mo video of your bat at impact, you will notice the walls flexing when it makes impact with the ball.  This is the trampoline effect of a composite bat.  Shaving a bat will create more trampoline and so will end load.  The more stored mass (end load) at the end of your bat, the more your bat will flex and rebound at impact vs a lesser end loaded or balanced bat.  This will cause your bat to break faster.    

7) What bat did you purchase?  Yes, manufactures make bats that are TERRIBLE.  You ever see bats with 30 day money back guarantees, well, these are bats that are known to be terrible out the gate.  Outside of these money back guarantees, there are still bats that are bad bad bad.  From a stock stand point, you can do a simple Google search and see reviews of products.  These are directionally accurate and can be applied to bat rolling as well as bat rolling is a break in process.  Shave bat reviews, these are only found on bat doctor websites and are largely skewed by the bat doctor themself.  I would look for sites that give real world reviews along with a personal review from the bat doc themself.  We are the only to my knowledge who offers both of these reviews.  

End all, if you were to call us up, all of our "answers" are guesstimates and based upon our own personal experiences.  Everyone is different and the truth be told, no one really knows.