Check the blue book price of the car, thats the most the insurance will pay. Compare that to how much damage that would cover (a broken headlight could total an old car.) Compare that to how much you pay for collision for that car. Digest all the numbers and decide.
Its a risk owning an older car that still has a lot of miles left in it, if someone else hits it, you'll only get a new headlight out of it, then a "totaled" title