Am I at risk?

I know this is a loaded question, I'm looking for informed opinions from the other TM owners here....

Our 2619 is an '08....should I change the Marathons now or give them another year? We're planning a couple long trips this year and I want the lowest risk possible of having a blowout. Sorry i don't have the codes off the tires to determine exact age. I'm leaning towards the Kumho's but don't want to waste money if not needed.

Thanks for any input.