Personally, I would change everything out this time. This way you get a new, perfectly matched set and know they are exactly the right length. I know I'm a little fickle about strings and cables and make certain they are in tip top shape. I like to change out every two years, even though my current strings may look fine. For the amount of shooting I do, with high end strings, two years seems about right for me. By then, I usually start to see some serving seperation around the cams and a little wear on the servings.

Its a peice of mind thing for me. Plus, you can get some cool color combo's to make your rig look sweet.