I never buy all the fabric for one quilt at the same time. I buy fabric that hits my eye and meets some quilt idea I have in the back of my mind. I am generally drawn to those colors that I like so have a good selection of mix and match in my stash.
I know what you mean about if you die. Our American Sewing Guild chapter is getting boxes of fabric all the time from widowers cleaning out their wives sewing rooms. Great for our charity work.