I don't really care what type thread I'm using to piece or quilt as long as it is the right color & weight that I want and my machine will behave with it.
I have used Fray Check to fix seams that popped in the wash. I wasn't always as consistent with my 1/4" seams as I am now.
I have and will continue to use good sheets for backing. What else are you supposed to do with a flat sheet that has lost it's fitted sheet?
I often piece batting for smaller projects from scrap batting.
The "stuffing" in my tablerunners is practice sandwiches from different quilting designs and/or threads.
I will shop at any store that sells cotton fabric and I will buy any fabric that is acceptable to my standards and is a fair price including used cotton clothing.
I bought a queen size acrylic blanket from the clearance aisle at Walmart to use as batting "in a pinch." Hubby thinks it's to keep my feet warm at night since it's laying across the bottom of our bed---ssshhhh!