Cycles Renderer - Updating Shaders and Images Every Frame? This question is more of a curiosity to the potential of increasing render times, however, after finding very little out about this anywhere else, I am thinking it may be an intentional feature.

I am rendering out a 60 second animation (1800 frames) and I have noticed that every frame that is rendered, it starts by updating the shaders and images prior to rendering the frame. My average render time per frame is approximately 4 minutes, about 1 minute of this time is spent on updating the shaders and images.

I am wondering why it does this, and whether it is intentional to the process or whether it can be avoided/rectified? 

I am using Blender 2.8.
For years this was left on the shelf because it was very hard to determine what was being changed and what wasn't between 2 frames due to the older dependency graph.
However recently Brecht and Sergey tackled the problem and the feature &quot;persistent data&quot; is going to make it into Blender 2.93.
You can read more information here:
https://developer.blender.org/rB50782df42
excerpt:

For Cycles, when enabling the Persistent Data option, the
full render data will be preserved from frame-to-frame in animation
renders and between re-renders of the scene. This means that any
modifier evaluation, BVH building, OpenGL vertex buffer uploads, etc,
can be done only once for unchanged objects. This comes at an
increased memory cost.

Here's some more information on the matter:
https://devtalk.blender.org/t/persistent-data-limitations/18427/2