These thin little plugs in a scooter make me nervous.
So, I've installed Iridium NGK's in my LIKE200i and the Liberty150i - and leave them alone for many months. My idle seemed stronger, smoother and raised the RPM's a few - which was reassuring when sitting for a light in heavy traffic.
Over-the-road felt no difference.
I did notice a difference with my LIKE's engine behavior when I tried the proper Denso Iridium. I went back to the NGK.
I carry new spares under the seat if needed....though can't imagine how I, Major Tom, would correctly diagnose a bad plug while out on the rural road, in the dark and rain!!
Stig