Every person i personanly know on a non boosted/nitrous LS runs TR6 plugs, with ZERO issues.
Hell my tuner buddie wont even touch your ride unles you put in a fresh set.
The only two reasons iridium and those type of plugs was made os because 95% of the population is too stupid to change their plugs or just to damn lazy to do it.
Second is the dealer ships got tired of wasting hundreds of thousands changing plugs under warrenty because normal plugs dont have a 1 million mile lifespan, combine that with first reason and iridium plugs were born.
I prefer to do a oil change and change my plugs at the same time for the cost of just the iridum plugs alone.
It takes me 10 mins or less to change them.