Isn't it funny here where I live it is almost always humid of some degree and Summer sewing can be a challenge with the plastic Solvey. So I like it when the Air Con makes it go a bit crispy makes for easier tear off at the end.
I keep mine in a plastic bag and in a wooden chest and have no problems at all.
Pleased you are able to use what you have as it is not cheap and none of us like to throw away embroidery supplies.
I wrap mine in a large plastic bag and keep it in a draw it is always soft that way.
How about storing it in a plastic bag first and then in a plastic bin? I wonder what others have to say about it.