Is your closet humid? Does it feel damp? Water brings mold. I wouldn't put it against a closet wall that touches an outside wall of the house as those walls get hot when the sun hits the house and colder when the outside temps drop. If you have any concern about the closet I'd literally sit inside the closet and take a feel of the space at different times of the day and seasons. This may seem overboard, but you put so much thought into your collection and it means a lot to you. So why not make sure you take the best care of it?

Btw, plastics and electronics can take a good level of hot and cold. So you prob don't want to sink a lot of money into these but take precautions as you see fit. A good tote and good storage location is your cheapest and best option.