Why render time in blender is increasing 10 times after rotating 3d model? I'm rendering  this scene in cycles (blender) on GPU with GTX 780 3GB
In preview mode it takes about 2mins to render 2000 samples.

In final render mode it takes about 40 seconds

But i need to rotate scene and render it from different view.
After rotation the model, render time has been increased to 20 times (to 20 mins per a frame)

But in preview mode it still renders for 2 mins


what's the problem?
Problem appears only after rotating the object. If i moove the camera and NOT rotate the object it renders for 2 mins. But I need to rotate the object and not moove camera.
I've posted at Blender's bug tracker and it seemed for first look as a bug, but 
Brecht Van Lommel (Rendering Software Engineer) explained:


  This is a typical issue with raytracers, many long thin faces along one direction are difficult to fit well in a BVH unless the faces are aligned to the X/Y/Z axis.
  Also, the workaround is to subdivide the object more so the faces are not so long.




After subdivision mesh along faces render time decreased much.

LINK to this discussion on Blender's tracker.