Look, its always better to study too much than not enough, and you need to realize that those questions are mini lectures disguised as a test. Especially in biology, the key is to remember why wrong answers are wrong. I have been looking through the destroyer sections more than once, but you must check yourself to make sure that you are not answering out of memory and you are really walking yourself through the logic otherwise your efforts are worthless. If you feel like you aren't able to see the same problems without memorizing answers then i would say move onto something else. otherwise keep banging away! why not?