If you're going to make an heirloom, why not use an heirloom-quality fabric that will withstand the test of time?
We love stopping in quilt shops when we're traveling, and to our local quilt shops. It's fun to touch base with other owners, compare notes, and talk shop. We also run into them and hang out with them at fabric shows, and that's a bunch of fun too. Oh, the war stories we tell! :-)
There's nothing like stepping into a really nice LQS, the smells, the displayed bolts, and the friendly people really give you a feeling you can't get at an online store (even ours) or a big-box store.