I also think the problem is that this was a traditional 100% cotton batting without scrim. This type of batting is meant to be quilted every 2". When that is done, washing every week is not a problem. I had a chance to examine one of my crib quilts 20 years after I made it, and it was washed *frequently* in the machine. The binding was worn in places, but the quilt itself was soft as a cloud; the batting simply got softer with each washing.
Tied quilts really benefit from a cotton batting that is needlepunched through scrim (such as Warm and Natural). These battings say that quilting lines can be up to 10" apart because the batting will hold its shape.