A grill that old working fine doesn't necessarily mean it's totally safe to keep using. If the non-stick coating is visibly worn or peeling, you're likely ingesting small flakes of it when you cook, and while the coating itself isn't considered toxic at low levels, nobody really wants to eat their cookware. The heating elements working normally is good, but that's separate from the coating issue. If the wear is just minor discoloration or light scratching, you're probably fine, but if there are actual bare spots or flaking, it might be worth replacing it or at least cooking with parchment paper on top to minimize contact with the damaged surface.