Unless the paint specifically states it is chemical resistant, things like salt and motor oil can start to stain and erode garage floor paint pretty quickly. The tougher the product the less damage it will receive, but even the toughest floor will start to flake and crack with prolonged exposure to tough chemicals. Mop it down every now and then and try not to leave chemicals, salts, and oils on the surface for too long and that will help to prolong the lifespan of the floor.