As far as the SSAT company itself is concerned, you can take the SSAT as many times as you like. Your target school may have its own policies, though–the best thing to do is to contact the school directly and ask what their current policy is on re-taking the SSAT.
Most top schools’ web sites seem not to mention the issue of taking the SSAT multiple times, which suggests that they don’t have a problem with it. Still, the best thing to do is contact the school directly and find out for sure.
It may be tempting to ask around and find out what other parents think, or what people in different forums or blogs are saying about about this topic, but the bottom line is that this is dependent on the policy of the specific school that you hope to get into, and what anyone who is not a representative of that school says about the topic is meaningless. There is no one-size-fits-all answer, so your best bet for a complete and accurate answer. is to contact the school directly.