There is a whole bunch of info on spark plugs on evo M but finding exactly the answer im looking for is like looking for a needle in a hay stack.

My question is the thread topic.
My step colder plugs are comming but im curious to know how long stockers last.
as of yesterday my cars become harder to start and 4th mid range and higher up she has a bit of a stutter WOT. I dont push her more at this point, but it only started recently. I pulled the plugs and they look good, stock gap 0.024... Possibly fried after a month of driving...

 

The stock IX plugs are fantastic. I drive my car hard, 30psi + meth. When I started maxing out the Green I needed to gap them a tad tighter. Now on the Red, still no problems.

I experimented with Denso IKH24 and honestly, I like the stock plugs better, even at 450whp and running 10's.

As far as lifetime, I don't know. I've replaced mine a few times as a precaution only, but never had them go bad. The longest I've used them is probably the set I'm on now, which is about 20k miles.

 

I had set in around 25- 30K miles...The mechanic said "oh these are bad", yet they look perfect to me ...Color = perfect...Tip condition = perfect...

 

I run 26PSI and have 40k on them no problems

 

It sounds exactly like a coil/wire issue.
I got a coil on plug from Sparktech, and now it is Smooooth!

 

They will go 60K on a stock engine. But, by then, there are visible indications that replacement is necessary. So, I'd say that half that mileage is reasonable.