When on a cycle, I try to turn the intensity way up. As you get to know your body, you get to understanding the "point of diminishing return" principle. Basicly put, when you get to the point where you are overdoing it.
For most bodyparts, all except bi's, calves, and abs, I train each bodypart once a week (when off gear). I blast them very hard, feed them, and rest them. It works for me. While on a cycle, I still go heavy as I usually would for the one workout that I would normally do, but I also add a workout where I am looking to use very strict form and go for a great pump. With the gear and proper nutrition, your body is able to repair itself much quicker and make better gains.
I use the pump workout strictly for aesthetics. Of course the core lifts are what you need to build pure mass. But the other lifts help with separation, vascularity, and simply put, a more aesthetically pleasing body. Regardless of how you feel about this, it is pretty hard to overtrain on gear if you are taking in proper nourishment. Liting heavy does have to be number one, but don't forget the pump!!