I have 3-4 specific types of quilts that require scraps. An X quilt (my name for it) that requires 1.5 inch strips and whatever size square I decide to use, puzzle piece quilt, and two others. When I make enough quilts that the pile of scraps starts to bother me, I cut the scraps to fit one of those categories. When I have enough scraps, I make the quilt.
I only purchase enough fabric to make specific quilts and don't really have a "stash." This works for me.