There are lots of patterns that you have to back track on so I don't think you need to worry about it. The only problem with stitching over a sewing line is that sometimes you can get a fabric wrinkle on the back. I just make sure my quilt sandwich is laying flat as I machine over a sewing line. I did a pattern where about six lines all intersected in one point, I did notice that this spot tended to volcano up a bit.