How much prep is too much?

<p>Hi, I'm an incoming junior and I will be taking the ACT and SAT tests in the fall and then in the spring if needed. I've started preparing for both tests by simply taking portions of each test every day. For example, I take english and reading ACT sections on one day, and then take math and science the next. While I do have detailed answer explanations and do find my mistake in every single question I get wrong, is simply doing this from now until whenever I become too busy too (1st-2nd week of school if last year was any indicator) enough? (Same thing with the SAT as well, but i do just half and half without writing each day)
I know there are many different forms of test prep out there but this seems to be my best option at the moment (I have a lot of free time and solitude)
Thanks!</p>

<p>I would periodically (once a week or every two weeks, maybe?) take an entire practice exam allowing only as much time as you would have for the real exam. That way you can get some idea where you stand and if you are making progress.</p>