I find for me that 5 days of weight training a week is too much. 3-4 days max is good for me. Don't get me wrong, I would love to lift every day but it would be overtraining. Like stated above it comes down to your diet, rest, level of training, etc. Listen to your body, if you feel if you are not fully recovering before the next workout then you are overtraining. Especially if you do say chest/tris and then are training shoulders but still sore from the chest workout.