Personally, I never use polyester thread for anything, but that's just my way of doing things. There's a special word for sales people who tell a customer they SHOULD use a specific product they are selling...the proper word is COULD. It's your choice, not hers. There is no real proof that poly thread will rip your fabric, but it will probably outlast it by a very long time.
ETA: I'd be willing to bet most longarmers use poly thread; I know mine does.
Last edited by ghostrider; 12-30-2011 at 06:40 AM.