Mike, you need to worry about the boxes not the trains. Here in AZ the boxes just fall apart. I've pulled boxes from attic crawl spaces that were so dried out they crumbled at a touch.
The corrugated boxes de-laminate. Labels fall off. The boxes and paper give off cellulose gas that reacts to bare metal, zinc plated metal, and to some paints and inks. (I commonly find nice boxed postwar Lionel locos with green scum on the valve rods. There are many Hot Wheels cars brand new in the blister pack with damaged frames and graphics from the outgassing of the cardboard.)
I have 4 prewar Madison cars that were LNOB when I got them in 1996. The cars got ruined because they were wrapped in the white foam used to pack apples and something ATE into the paint. The boxes were complete with all flaps, but now the flaps are just falling off.
After seeing the Madison car boxes last spring, I sold a bunch of the boxes I had and kept the trains. God knows what is happening inside the file box of old catalogs. Those might be in a plastic box. Does that make it worse or better?
Think about this. . . I packed my trains up and moved them from one air-conditioned room to another. I packed them in Feb/March of 2019. All the early period trains were unpacked by April 2019. I'm still unpacking the trains that go on the layouts now in June 2021. The newsprint is dried out and easily tears. The older paper in boxes packed 2-3 years ago is falling apart.
I tried years ago to get an archivist to do an interview with me years ago about preserving these old toys, but couldn't find anyone.
