I'm sorry if I misunderstand what you meant, but are you saying that it took 3.5 or 4 hours each frame?? BTW I also understand that you use AA of 16?
If so, let me tell you: that, is an extremely high setup and render time. rarely I use AA 8 or higher. if you have noisy renders, there is something in the scene that cause it. maybe you forgot, or you ignore it, but there is many ways to optimize any scene in TG: for example check the atmos quality, if you are using fog, check there is an excessive setting or unnecessary like "recive shadows from surface" enable or "cloud quality" in 0.2, for example. GI settings can also very problematic. I dont know, just to keep it in mind for your next animation, assuming I understood correctly what you meant