I guess no one does this. I think I did once. While loading some exposed film onto the developing tank reels, the red heater lamp on my Jobo came on, and I realized then that I'd forgotten to cover it. I had some shots on that reel that should have had some deep blue shadows (Velvia in shade), but the shots came out rather nicely. I never went back to test my impromptu heater-lamp-post-exposure-burner, but I haven't been worrying about covering that lamp anymore.