Are you talking about just regular piecing? or Machine Quilting? I go thru many bobbins when machine quilting. 10 to 12 in not uncommon with a large quilt. It will depend on how close together the stitches are. A big meander will use less that a tight close stitch.
Also I moved the stopper on the top of my machine to make more thread load onto each bobbin, but I still have to change often. Maybe it is so we have to clean the bobbin area each time we change bobbins...