Indeed.. But it's the only way to know for sure.
Just like were "Suposed" to check our tires, lights, oil etc, every day. At least I remember being taught that, when I was being trained to drive yellow van's arround the town for a living.
But juging buy the number of cop-cars with a light out I've recently seen (or the same one has been following me arround the country!) Even they don't do that now.
Regards...
Dave B.