i dont notice any difference in running a different plug but i do run the BR8EV . now that i got my jetting right i only change them out every month , just for good measure . IMO it cant hurt , plugs are cheap .
S.D., According to NGK.com, the EG is the same material as the ES but a thinner electrode. The EV is Gold/Palladium electrode and thinner yet. The EVX is Platinum electrode and thinner than the EV. The EIX is Iridium electrode and the thinnest of all. Supposedly, the thinner the electrode, the stronger the spark is even though the heat range is the same. The thinner ones are supposed to give more power and efficiency due to a stronger spark and more complete fuel burning. I was wondering if anyone could confirm this.
I think I changed my plug once. Not sure though, might have put the same one back in. If your bike is jetted right it should be easy on plugs.
Same with my kids kx60, although I am sure I have changed it once.
And it has about a billion hard hrs. on it, And a few mins. under water.
I used an EVX (The platinum one) I had fouled about two or three stock plugs and I switched to the evx then I changed the plug once a year for three years just to be safe I never fouled one of the EVX plugs. I was doing a lot of jetting changes at the time I switched so it is hard to tell a difference the plug alone made. Being reliable was the selling point for me.