Hey OP, I understand your question, but this isn't exactly worthy of its own thread. I'll break it down though. You see, all drugs effect all people differently. Are you familiar with the concept of a bell-curve? Well it essentially explains everything in the clearest terms. While everyone is different if the fictional "objective" peak of effects was 3 hours, our bell-curve will demonstrate that most people are going to experience it within mere minutes of that objective peak, get me?
For some 2.75 hours. For others, maybe 3.25 hours, but it's not necessarily going to vary much more than that. You can generally use an encyclopedia resource which will give you that objective peak. From there, draw your most logical conclusions, yes?
I'm gonna close this one. There is no more concise explanation than educated guessing. Another poor still-born Bluelight thread. It never even had a chance.