Those plugs are quite nasty.....Used it and only lasted about 3k miles.....then for some reason ALL the plugs got fouled. Switched to Bosch platinum +4 and they're working much much better.
However, stick with iridium plugs. iridium is supposed to even harder than platinum, which means more durable. However, poor construction of the plugs also play an important role in plug performance.
Split-fire is a fine example of poor plug construction.
My 2 cents