heirlooms are handed down- generation to generation- not necessarily a quilt- any item that is saved/preserved/protected and handed down-
if you make a quilt, give it to a family member who then puts it away- gets it out once in a while to show it off, refold it and put it back away- then they give it to someone else---it is an heirloom- they are not all made with the intension of being an heirloom- and some people may look at it and say...."really- you saved that?" and some generation down the road may really really love it- care for it- keep it to pass on- someone else may see it- say--"hey, this will work to cover the wood pile- no one's using it anyway"
happens all the time .
like everything- an heirloom is in the eye of the beholder (as is the value)