Well, i don't lift any more than i can handle, i don't push myself too hard because i know that would seriously mess my body up. Maybe i should try the twice a week thing and see how that works.
Hey man, pushing yourself is what its all about! If you arent sore as hell after lifting, you wont make progress. Its that simple. Do you exercises as hard as you can, feel your muscles tearing, then eat loads, and get some rest. But not pushing yourself to hard makes weightlifting basically useless- no matter what goals or aspirations you have, it is going to be hard on your body. But when you start to see results... thats when addiction happens. So don't worry about messing your body up, use good form, and rest and eat, and you'll be solid.
Also, when I did a body part split I did it like GSP, I worked muscle groups twice a week, saw great gains as long as I was busting my ass on each and every set.
I heartily accept the motto, "That government is best which governs least"; and I should like to see it acted up to more rapidly and systematically.