In my animation I'm creating a looping Cumulus cloud that fades over time and a copied version of itself that transitions in so that the end matches exactly with the beginning. To do this I have animated several parameters but mostly I animate the "Coverage adjust" so that the cloud, at start, looks like it's fading away as the other one comes in.
For the most part this has worked, though the scene gets darker as both clouds are merging ontop of one another, which is to be expected.
Here is something I noticed just today though. When I copied a cloud node, with/without animation applied, the quality changed 9/10 times. (See images)
I did not change any parameters and things changed. This first image quality was set to "0.300192 (for quick rendering) and when I copied the node the quality changed to "0.0186866". I thought this maybe due to the low quality setting I started with but when I started with Quality "1" the setting still changed when I copied the node.
Hope this helps a little.