We know that exposure to light and heat burns out the luminescent property of phosphorous, but I found something else. It wasn't so much an experiment as a discovery.
I used to paint with phosphorous a lot, phosphorous mixed with acrylic medium mostly. Stars, cities, things like that. For one painting I taped a magnet to the back of the canvas and threw at speed a mix of phosphorous, steel shavings and acrylic medium at the canvas, at the magnet. When it dried, which was just minutes, the phosphorous surrounding the magnet was completely burned out. It never glowed again. I had not seen phosphorous burn out like that before. It wasn't heat or light.