only really need to run colder if you're having issues with pre-ignition from the plug tip staying too hot
all you need to know
http://www.ngkspark.com.au/sparkplug_tech.php#I really do not see any point in paying mega bucks for fancy plugs.
the fanmcy plugs have very tiny electordes (0.6mm) if you suffer any abnormal (and normal) detonation, they electrodes can pit very easily,
and commonly destroy the end of the electrode. this increases your plug gap and you'll get mis-firing. thus wasting your $20 plugs
Also, the iridiums/ platinums ll seem to be gapped at 0.9mm... which I feel is too big for modified boosted engines
0.7-0.8mm is my preferred gaps (hope you supercharged H6 Owners are closing up the gaps on your plugs)
the copper/ nickel plugs have a 2.5mm electrode ande is much less of a chance of detonation having a largeeffect on the plug gap.
a set of plugs takes 30 minutes to change, do them every 20,000km.