Anime-Beta TNG

I collect color concepts from various series' and films. 99% of the time, the concept art comes with a piece of plastic (likely a blank cel) that has been cut to the size of the art and then 'hinge' taped so that it covers the painting. The artists did this to protect the art. However, I worry about the acetate or tape damaging the art as it degrades. Has anyone else seen this? If so, and assuming the art is going to be kept in a mylar/poly bag from now on, do you remove the acetate?

Note: The color concepts I'm talking about are usually paint on paper or board of some kind, not on a cel.