I used to run them a long time in my cuda...at least a year or more. No reason to change them all the time. I use NGK plugs and MSD 6AL boxes on all my cars. Plug wires vary, never had a set that didn't run good, some just fit much better than others.

The E3 plugs are a joke...along w/ every other "revolutionary" plug design. There's so much snake oil in the ignition products market it's ridiculous...plugs AND wires. There a lot of gimmick parts out there, but the ignition system market seems to be saturated with them. Maybe I shouldn't say "gimmick", but a lot that work fine, just never live up to their hype.