Schedule for LSAT prep

[vitamintime]

So I've signed up to take the test in June, and about three weeks ago started taking preptests and going through books like Princeton Review and Powerscore LG Bible. So far my preptest scores have ranged from 157-166, so I obviously have a ways to go before I get what I want, but I'm concerned about burnout. At the same time, I'm also worried I won't devote enough time to studying near April, because I'm still in school and finals will hit around late April/early May. I'm not taking a prepcourse because I don't have the money to shell out, so most of my studying will be self initiated.

How much should I be studying now? Should I even be doing these preptests, or should I wait until March or April at least?