Fabrics are dependent on seasons, fashion, fads, (quilting, although may be everything to you, in the textile world it is a really small nitch) most lines are released for 6 months, then replaced with what is new. Sometimes a manufacturer may receive enough feedback, requests that they will rerun or rerelease a line, but they generally want to move on and keep up with current trends. If they believe they have a (timeless) design they may keep making it for a time, until the orders dry up.