I frequently stitch with a polyester thread and haven't had any problems. I don't wash my quilts any more than I have to.
A lot of quilting with a curving design, will stabilize the blocks with all those seams and will help your quilt last a long time. If the seams can move and the polyester thread can saw at the cotton fabrics, then it is likely that you will eventually have fabric failure. I have had fabric failure with a 40 wt cotton thread. It has been washed 20 or 30 times and the quilting was more sparse than I have learned to do. Do not quilt in the ditch as straight line stitching. Do some type of curving pattern that will support the 3 elements staying better without placing stress on any single parts.
fyi....For my first quilt I did a minimum of quilting as per the batting suggested spacing and did them as straight lines. As I pulled the quilt up the first night of use, I heard seams popping and quickly realized the error of my ways. I added some curvy seams and tried pulling the quilt up again. I didn't hear those angry seams popping and quickly learned a very important lesson. Seams stitched as straight have more stress when pulled than curving seams.
Last edited by Barb in Louisiana; 08-20-2021 at 07:09 AM.