On this forum, I have often seen the phrases like "I'm not making an heirloom quilt". To me, it seems what the person is usually trying to say is that they are making a quilt that they are perfectly fine with getting hard use - e.g. going to the beach, letting pets sleep on it, or what ever the owner might possibly want to do with it. They don't expect the quilt to be pampered and are fine with it eventually wearing out. The quilt is intended to be used well and thoroughly enjoyed.
I think of heirloom quilt (as people use the phrase in this forum) of a quilt made with higher than average quality and care that is expected to be used gently, and will hopefully last for many, many years. So the quilt is fine to be used on the a bed and laundered regularly, but it would not be used for picnics outside. I don't think people who make these higher quality quilts intend for them to be sitting in storage, unused, but that does sometimes end up happening.