Those plugs are looking pretty carboned up for 25 hours, not quite at the light tan color that's desireable. What is your EGT in cruise, and what type of instrument are you using to measure it?Also, are you premixing oil or using the injection system?Is this the condition just after returning from a flight, or was there considerable ground running time before you shut down?
In the pic the colour is a little bit darker than real, the color is between brown and light brown, I think, it's pretty good.

In cruise I have about 1150F and I use the rotax EGT instrument to measure it.

It's an injection system and it burns 13-14L/hr during flight at 5500-5800rpm

The condition is after a flight about 50 minutes before shut down.

http://www.cfisher.com/152hournkg.html
It works more hot (EGT) than mine, isn't it?


Olaf