The paper conservationist I mentioned in an earlier post brought up some interesting points/problems that he has seen in his years of working in the field. These were mostly related to "acid free" materials. He has seen slipcases made with acid free paper and cardboard but put together with a glue that was not archival quality. He said he has seen problems with transfer of the glue to the book and dj with adverse effects. He said also to be aware of mylar dust jacket covers that have acid free mylar and backing paper but joined with non-archival glue. He said he has seen some of these have problems with glue transfer to the dust jacket they were supposed to protect.
I'll have to read the descriptions for BroDart and DemCo dust jacket protectors more closely. I honestly have no idea if they use archival quality glue or not.