I know this is an old thread, but per APQS on their "Turn Your Passion Into a Successful Business" brochure:
"Heirloom Quilting is dense, heavy quilting, often including specialty techniques such as trapunto, micro-stippling, tight crosshatching, feathers, very intricate free-motion designs, stitching-in-the-ditch, small background fillers, custom block/border motifs and more. Heirloom quilting can take anywhere from 10 to 40 hours per queen-size quilt."
I don't necessarily agree with that definition, but I think it applies to the original question.