6 years does not sound like a long time for having those tires. But, from your description I would replace them. You would greatly decrease the chance of a blowout/failure in the middle of nowhere. Having them replaced at home means you can pick the place. AND. No worrying about old tires means a more relaxed trip.
I have Toyo's on the front and Kumho's on the rear. I am happy with both.
Michelin's and Goodyear's are good but way overpriced in my opinion.
Whatever you choose-----keep the rubber side down and the shiny side up :)