It really depends on the individual and how your body handles it. I've heard stories where guys run it for 16 weeks..8 weeks. Lot of different scenarios. 8 to 10 weeks I think is good.
I've run tren A for up to 8 weeks before I tapped out at 600 mg. But when lowering to 450 give or take, I've stretched it to 10-11 weeks before I was ready to call it quits.
Most of the time your body will use an anabolic compound for 5 to 6 weeks before it stops using it so much, something to do with homeostasis, so maybe if it is like a 12 week cycle switch to npp for another 6 weeks or something else anyway.