if you have arcing wires then theyre bad.it doesnt matter how new or old or what brand they are.ive been a mechanic for over 30 years and it doent matter where you bought them or how much you paid for them,we get bad new parts every day or they don't last long,its just the way the world is.i really think your overthinking it on the plug wire problem.it may not be your problem that your having but seeing arcing is not a good sign.