The reflection of this boxes are giving the impression of two light sources like windows or big white panels which are used also in the field of professional photography. You can notice that image 10 is a little bit darker than image 12 even I did not change the light settings. Why this?
Whenever you enable final gather you will notice that self illuminated objects are able to create light. The bigger your self-illuminated object, the brighter the surface close to it will be. That's why the rendering in image 12 is a bit brighter. Be careful with the size of the 2 boxes, don't make them too big and don't place them too close to the teapot, otherwise you will create too bright areas. At this point you can do a final rendering. This means you must set all settings to the maximum values, in this way you will have a perfect rendering. In the render panel (image 6) set Minimum samples per pixel "4", maximum "16”. If you change the BOX filter to "Mitchell" your rendering will be a bit sharper. The minimum size of a final rendering should be 1024*768 pixels ( bigger is of course better). Don't forget to increase the shadow samples (area light sampling) to 32 or better 64, in this way your shadows will be perfect. Put in final gather sample slot 300, if this is not enough put 400.
Now make your final rendering.
The result of the last image is already very good, but we can improve it. I also teach to my students that Photoshop is a tool which is able to improve a rendering in many different ways. Let's apply a glow effect to our highlights ( in our case we will assign a glow effect to the reflected boxes on the teapot to give the impression that there is a lot of energy coming from the white panels). Select the "magic wand tool" to create a mask on the brightest parts (which are in this case the white boxes) of the teapot surface like in the image below.
Now press on your keyboard CTRL+C and than CTRL+V (copy and paste). You will see in the layer panel (F7) that automatically you have created a new layer on which there is only the masked part of the teapot (see the image below).