Yes, there is no way to know that they are in the same situation - which is contaminated and with lots of their accumulated carbon deposits !!
And the worst is that there is no "sensor for carbon deposit" in your machine!
This in turn becomes a problem only when the car starts to lose dynamic performance or at least see a signal on the "Check Engine" dashboard and your vehicle coming into the emergency mode conditions happen for various reasons, but the question is how to handle the problem or how to prevent it ?!