I'd be far more worried about mixtures when the bike is making power. There are minimal forces and temps in the chamber at idle. Combustion conditions are the most severe when under load at throttle positions higher than idle.
Your center electrode insulators are completely white as far into the spark plug as I can see in that picture. This means combustion temps are very high, very deep into the plug. These kind of temps do not occur with an air cooled motor at idle settings. They occur when the chamber is making serious power and heat, faster than the spark plug and engine cooling fins can remove it, and thus there is electrode surface cool enough to allow deposits to form. Such temps, far away from the combustion point of origin and closest to the heat dissipating surfaces, infer temps at the piston crown and electrode tips are near the limit of endurance. Once these points encroach into the "glowing ember" region, you get pre-ignition, then detonation, then engine damage. Premium fuels may save your motor as it is more difficult to ignite than regular. But, if your CR is low enough to operate on regular fuel, you should make the upper throttle setting mixtures richer, so the chamber temps lower some. Colder plugs may help, too, unless your cooling fins are already taxed to their heat transfer limit. Have you driven this bike in hot weather, yet? What is your air density? (elevation and temp?)
It's your bike. So, of course, do what you want. But, don't say you weren't warned when something goes bang.
You can change you idle jet to get some soot onto the plugs at idle. But, then at higher power settings the soot will burn off and the idle jet will not make much difference in chamber temps at those higher settings.
Good Luck!
