Joe,
I have been researching the same thing. If you read Iron Man's thread in the articles section regarding his routine, you will find some answers. It will depend on how many sets are you are planning per workout/exercise and how deep that runs into your recovery ability. I know personally I cannot recover from deadlifting twice a week, but am surprisingly recovering nicely from squatting twice per week. So some will be personal. I am tending to find that one exercise is better than two per week, which is not what I have been doing. I was doing two per week. Go read Iron Man's article and see what you think. He advocates finding the "best" exercise for each bodypart and milking it hard. I think you will like what he offers.
Did you get this routine from Brawn or Beyond Brawn? I have both books and refer to them often. I'm getting up there in age and it seems the Iron Man and Stuart McRoberts approaches are working thusfar.
Take care!