Backstitching and stitch length
It is not necessary to backstitch at the beginning and ending of each seam. When you sew the next piece in place it automatically locks that seam in place. If you are using a smaller stitch length as you sew it also helps. From the right side of your pieced blocks when you pull on the block, if you can see your stitches between the sections your stitches are too long, so just shorten your stitch length and you will have a much stronger seam. I have quilts that are 20 plus years of age that I made and they have been washed and handled many, many times and I have never had a seam turn loose because I learned over 30 years ago that it is not necessary to backstitch. And leaving at least 1/4" of thread at the start and ending of each seam is very good.
Gitlisgal from Oregon