I don't make a quilt with the intention that it becomes heirloom, but if it happens to last and be cherished from one generation to another, that would be fine.
The issue kind of reminds me of the situation with baptismal gowns for infants. You can make an "heirloom" baptismal gown that is meant to be used from one generation to another. However, some babies are baptized wearing blue footie pajamas. If someone wants to keep those common footie pajamas for the next generation, then they become an "heirloom" that is meaningful in their family.
As I said, I don't make quilts with the intention or expectation that they become heirlooms, but if someone wants them to be, that is their call. I do try to make them sturdy enough to last as long as possible.