I had all my Lionel trains from the fifties and accessories stored in my attic for a lot of years. The temperature up there can get to 120 degrees + in the summer. The only engine I had was a 2026, but I had the coal loader, cattle car and corral, and a few others.
I only became interested in trains again two years ago when my little grandson became obsessed with trains. So I dug them out of the attic after baking up there for 30 years or more (my mothers attic before that wasn't as hot).
Everything worked with a little maintenance and service. None of the plastic had melted, etc.
Now I have some modern electronics equipped locos and cars and would never store them in a place like that. Newer trains would never survive and I run them periodically to protect parts that can't be replaced. This is a different era.
John
