I believe it depends on how you define "heirloom".
Is it the appraisal quality which involves the workmanship in the piece or
The emotional value of the piece.
Traditionally I believe the workmanship in the piece determans the status of heirloom.
The Natioal Quilting Association has a special category of "Master Quilter". The quilts that are judged in this category are certainly heirlooms.