I agree with Manny. Basically your wires and cap ought to be good for 50-100k miles.
As young hot rodders on damp nights (all nights were damp since I lived near the water in S. Texas) we used to raise the hood and rev the engine. If there was the slightest high voltage ignition leak you could see the spark dance all over the wires.
I don't know about a grown man spraying water on a high voltage ignition system. Isn't that kind of like pissing on an electric fence? The idea seems interesting after a few beers, but it doesn't take you long to figure out that it really wasn't that clever. I sound like I speak from experience.