When I started quilting almost 20 years ago a friend who was a great mentor for me said she let's the quilt tell her how wide to make the binding. Some quilts look great with just a narrow strip to frame them. Others need a wide binding to stop your eye at the edge of the quilt. Some need the binding to blend right in with borders. Others need an additional pop of color on the edges. I like to lay some folded pieces along the edge and just look at them for a while before I make a final decision. One thing I always do is to keep all my extra fabric with the completed top so I don't accidentally cut it up for a new project. Bet you can't guess how I learned that lesson! LOL