I am a longarm quilter and use sheets as backing all of the time with no problems. My APQS Lenni can not tell the difference between sheets and quilting fabric. I quilt them all, all cotton, poly/cotton and flannel. I won’t use microfibre sheets as I don’t like the feel of them. Sheets do not warp or break my needle and my needle has not broken or warped the sheet. For me, sheets make a very affordable backing for quilts that are going to be used every day. You would need to choose a sheet that wasn’t as tightly woven for hand quilting or say a lot of bad words trying to get your needle through easily.