My grandmother kept hers in the basement next to the furnace for probably 15 years, and when I finally dug it out as a kid, the whole thing worked fine. The problem was the black paper sheets, they had gotten damp and warped just enough that the pegs wouldn't push through anymore. Nobody ever thinks to check the paper because it looks okay sitting in the box. Once I swapped in a fresh pack from a craft store, it lit up like new. So your "broken" Lite Brite might have just been a paper problem the whole time, which is a strange thing to realize two decades later.