As a maker of prayer ropes, I'd encourage you to keep using your current prayer rope unless it's either falling apart or you've become overly attached to it.
That last bit sounds odd, I know, but I have a tendency to get attached to the prayer ropes that I make for my own personal use. When that happens it's usually a sign that the Lord is about to put someone in my life who needs a prayer rope, and I end up passing my personal rope along to them. Then it's months before I finally take the time to make myself a new one.
Signs of wear on a prayer rope are like signs of wear on a Bible, in my opinion. It makes the item unique to you and almost an extension of yourself. Wear on your prayer rope is a sign of growth in your life with the Lord.