I attended most classes first year, but I'm seriously considering stopping for second (I know many people that stopped mid first).
Part of the advantage is that you're much more efficient on your own, you dictate your schedule instead of waiting for the lecturer to dwell on points you got quickly, or answer questions that have no relevance to the topic at hand and then sit through the 10 min break every hour.
Also, you much more fresh when studying the material. You aren't tired from sitting through 4-6 hours of lecture and if you're not a morning person you can start later and work later.
BTW. that 6+ hours seems a bit low, esp if you're skipping lecture.