I change belts every 50-60k miles and that's it, what I use on your LLY Duramax. It may be too early to change, but I feel better knowing that I probably won't get rejection. If the belt breaks, you will be in big trouble. Take a spare tire and a belt change wrench with you. Worth it. Gas stations don't have a clue and give them a belt to use. Also, I've seen some nasty pictures of what a belt can do when it snaps on the freeway. I'm just saying.