You should probably think carefully about whether you can really get a significantly higher score this time; you have tested in the same range three times and, as you've noted, you have "a LOT" of things to do. Obviously, if you are wedded to the idea of going to a very top school, you do need a higher score. I'm not sure, however, that all schools will disregard your lower scores (since there are three of them), and a higher score may not guarantee you admission to Harvard or Yale. It's hard to say how schools will look at these scores since they probably see very few people who've taken the LSAT so much (since you are not permitted to take the test more than three times in two years).
You've already gotten into very good schools, and I don't think most people would forgo the opportunities you have for such a crapshoot. But of course no one can tell you how much of a premium you place on going to one of the top five.