Think of your stash as being like the food in your cupboards or toilet paper. You'll always need at least some on hand until you die. You wouldn't want to run out of food or toilet paper, even when the end is near.
Some fabrics are like eggs or ketchup. You always need a supply on hand of, say, a solid white for applique background or a green tonal for leafy-looking pieces.
And some, like take-out Chinese food, are for a specific purpose and you don't want them lingering around forever.