I totally agree with what everyone else has said, so let me offer a different take. In the past two years, I've downloaded the audio for every lecture (I'm not a class-goer) so I can tell you that in two years, I've listened to 600 lectures. We get 5 or 6 weeks to study. That's 100 lectures per week, if you give them all equal time. Break that down to 14 lectures per day, which is insane. Or, if you wanted to go by slides-lectures here are generally at least 50 slides. If you worked 10 hours per day, without breaks, that's a little more than a slide per minute. This might actually be within the realm of possibility (though I'd personally freak out within a very short time), but all of that would be spread over information that may or may not be relevant. Alternatively, you can spend all of your time on a review source (which you still won't be able to memorize entirely in that 6 weeks), but it'll all be important information.
That's why nobody studies from lectures. They're good for reference sometimes, though!