Well yes. If you want the object to be visible like the light on top of a police car you leave some ambience on or it turns black. It may not be 90 you want. You will have to see how it looks with your current light setup and decide. If you want some pin prick to completely disappear you could toggle the transparency. The thing is transparency eats more calculation time and real lights go out, not away. The other thing I advise is save a whole other scenefile now under a different name. The reason is I have animated textures before and when I delete a keyframe the motions disappear but texture animations remain. It's hard to undo changes when this happens. I'd make a file to play with where you can feel comfortable about trashing the whole thing and start over on the animation. If you decide the flash is too fast it's going to be hard to back out of a minute of frames. better to trash and restart. Save early and often.