5min every 20k isn't much haha. Like I said, for a higher boost application you want better spark. If you're staying stock, just get regular iridium.I my self have better things to do than to change plugs every 20000 miles (Been there done that) when for $30 more i am good to go for 100000 miles.
Not to disrespect your experience, but most mechanics are just that, mechanics, knowing how to repair and swap parts. Performance building is a while different game. I don't take my car when it has regular problems to my tuner, nor ask my mechanic to install and work on performance parts. I didn't do those upgrades for the plugs, I did the plugs to support the mods. 1.5 hours for a plug job is highway robbery. Even a novice should be able to make it a 30 minute job.Non of those changes would improve R&R of plugs being an ASE certified master mechanic with 40 years experience i would say on a good day from start to finish 1 1/2 hrs this includes gathering tools, covering fenders, removing cover, R&R 8 torx screws, blowing out plug holes, R&R plugs, lubing with anti seize the threads torquing to 15 lbs . Do not leave off the torx screws as the coils will vibrate and go bad quickly.