too often. I think i'm done with it for a while. I use it for strength and I've come to learn that if I take it any longer then 5 or 6 weeks it eventually starts to cause me to go backwards. It's like there is this period where I will peak with it, then everything goes to hell after that. On top of losing strength, my tendon's and body feels fucked up and my mentals state goes to shit too.
For bodybuilding purposes and that style of training I'd say run it as much as you want as long as your staying healthy.