Administered LSATs are remarkably stable: when a test taker retakes, generally scores half the time improve and the other half decline, but rarely by more than 3 points (less than half a standard deviation).
That said, perhaps almost everybody who cares enough about the LSAT to retake it prepared thoroughly for both their first take and their retake. And anecdotally, most people end their practice doing better than they began. Conclusion? You can get better, but only to a point. How much better? Not clear. We could look at the advertised score gains from test prep companies (as we could suppose that such a number is highly scrutinized, and at the same time, based on the low end off of cold first takes). On the SAT at least, they're widely reported to be an average of less than half a standard deviation (the equivalent of about 2 points on the LSAT). (source:
http://online.wsj.com/article/SB124278685697537839.html But a test prep course is not intensive repeated practice, which probably has the best result. And maybe not all people who take SAT prep courses engage in intensive repeated practice (perhaps some take the course merely because their parents made them.) Maybe the throughness of preparation is normally distributed and correlates to score gain; in that case, the outliers preparing the most account for the highest score gains (and the data do show that some retakers of the LSAT do score much better). Or maybe students who take test prep courses do engage in through practice, because their parents make them do that too.
We could be pessimistic and reason thus: people who retake their LSAT do so because on the actual LSAT, they scored lower than their higher practice test scores. These are the most motivated, so they engaged in intensive and repeated practice, but (usually) did not receive a significantly different score. This would bode poorly for people who have not yet even had a higher practice test score and would suggest a "discount" to their best future score increases vis-a-vis their actual score.
We could be even more pessimistic: perhaps, however, most people who retook the LSAT took it cold the first time, realized they didn't do well enough to get into a good law school when they thought they would (as most do), then engaged in intensive and repeated practice before taking it again. People who do well on the LSAT have some incentive not to retake it; people who do poorly do not, and there are surely many people who do poorly taking the test cold who thought they would do better. This reasoning would bode horribly for score improvements.
But this still doesn't give us a number. I know of one person who experienced an increase of a standard deviation (i.e. 7 points) or more. Many people in this thread will report even greater increases. Others will privately admit they experienced a decrease of a standard deviation or more. But anecdotes just simply aren't a substitute for data.
So, horseshoe and hand grenade it? 170? Probably not. But 162? Maybe. Maybe 180...keep on practicing. It's important enough to give it a shot, even with no guaranteed increase.
Now another thing: large score variations, in my experience, are all mental. Something physiological during the actual test can simply make you smarter and more alert. It's "fight or flight." I think if you can get yourself in that mode, and then, instead of "fleeing" (i.e. panicking), manage to maintain your focus (and "fight"), you may be pleasantry surprised.
Now one more thing: focus on strengths. My biggest gains came on the sections I was already best at. There was a clear work-reward imbalance in my practice favoring the sections I was already strong on.
TL;DR (It wasn't that useful anyway) Just practice and see. Answer through experience.