Colleges evaluate the SAT I in different ways. Some will take your highest math and verbal scores even if they were earned on different test days. Some will take your highest combined score on a particular day. Some will take take the average of all your scores. No matter what each school's policy is, every single score you earn is part of your permanent transcript, and the colleges see them all.
Therefore, it may not be a good thing for you to take the test as many times as you can. You should only take the test when you believe you are truly prepared. Ideally, it's better for you to earn your highest score sooner than later.
You can take the test two or three times, as long as your scores will be considerably increased each time. However, if you hit 1800 or believe that you have dig out the highest potential you will ever have in the test, you'd better stop there. You don't want your next possibly poorer scores to drag down your average score. On the other hand, if you are confident that after more practice, you will do better the next time, go for it. In other word, it'll be meaningless to re-take the test if you expect to earn about the same or poorer score every time.