I don't like the spraycan suggestion. It's frustrating if you shoot someones tires and he fixes his car at the spot, in real life you can't do this either so why should you be able to do it now? I know it might be tough/annoying, but it's part of the game to visit the pay n spray regularly. This also counts for the 'heli more health' idea, learn how to handle the heli, if you can't just leave it at the ground.