been using poly threads for 40+ years...i've never had anything fall apart---
i've over the years just shook my head and walked away when i've heard from the *quilt police*
that you should never use anything except cotton thread...i personally hate using cotton threads- for me they are a huge waste of money because they break every couple inches- i do use them up hand basting- but what a waste of $$=
although i do know some of (those who would never use anything but cotton) who use it successfully- just not me--
now days i use lots of different threads, poly, poly blends, silks, rayons, wools---pretty much anything except cotton- unless it's a blend.