You may write the test as many times as you like, but you cannot take the LSAT more than three times in a two-year period. Some schools average all of the scores, while others take the most recent or the best score. Check with the regulations of the schools where you are applying to find their policies on multiple LSAT scores.

If you write the test and get a low score, you are at a definite disadvantage when applying to schools that average your scores. For example, suppose you scored 140 on your first LSAT. Even if you get a high score of 166 (94th percentile) the next time, your average score is 153. This is barely above the national average in the U.S., and lower than the average score range of successful applicants at many law schools
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Your best bet is to write the LSAT only when you are consistently performing at your target level on test simulations. In order to conduct a proper simulation, you must take the tests from past years under realistic conditions:

1. The whole test should be taken in one sitting.
2. Choose the order of the multiple-choice sections at random.
3. The time allowed for each multiple-choice section must be the same as on the actual test (35 minutes).