I have toys from the 80s that are now dull in color and the plastic has taken on a brittle feel, and they haven’t been handled that much the past 30 years.
Conversely, the plastic on my garaged 80’s dirt bikes still is attractive, shiny and flexible. So are the seat coverings. But time does take a toll on rubber seals and tires (tires replaced due to sidewall cracking).
We’ve got some HO gauge trains stored away that were boxed up 50 years ago. Looked a them a couple of years ago and they appear the same as they did back in the day.