Years ago I would lift for close to two hours, doing two body parts each workout, but I was drained to the point that the second body part I was hitting was getting cheated because I had no energy. Yeesh, that was a mouthful. It depends though. If you only want to lift four days a week and no more, then you are somewhat trapped into doing two body parts in one training session on some days, which will certainly be more than one hour. The drawback is possibly being a little tired in the middle of your extended workout; the upside is that you have more days off to rest and grow.