Tips for Good & Fast Blender Cycles Lighting:
1- Use 2~4 light bounces.
2- Use Light Falloff node.
3- For Main Light, set it to "Quadtratic" with little/no smoothing.
4- For the other lights make it "Constant" with high smoothing value.
5- Using anything other than Quadratic with zero smoothing gives a physically incorrect result but clears the noise very fast!
6- Composite the final render with a little glow to make transitions between highlighted and dark corners smoother.
I hope you guys find this useful