Movie projectors put out lots more heat than the average slide projector, which has a fan to whisk the heat away. I wouldn't use a slide projector with a broken hot mirror, which reflects IR but lets visible light pass, but 1 minute in front of the bulb shouldn't affect it too much. An hour, on the other hand, according to the Wilhelm Institute, would fade Kodachrome, where the Ektachromes and Fujichromes can spend 2.5-3 hours in the projector before they get a similar amount of fading.