Stash: conceal; put in a safe or hidden place....hoard, store (Concise Oxford Dictionary)
I don't have a stash. I think of it as an Art Collection.
My fabric, yarns, fibres threads etc are all displayed in clear blanket tubs. True, they are in the loft so are in the dark most of the time - but that is for their protection. I store the paintings made by my DH in the same way, and also my sons sculptures. Every so often I put into the loft the ones which have been on display, and select some others to bring down and display instead.
I love to browse in my loft. It has an easily accessible ladder so I can go up at any time. I revel in the sight of so many beautiful colours, enjoy the sensual experience of feeling the silk, cotton, wool, alpaca.
I don't have to have used it to make things in order to enjoy it, just as one doesn't have to have eaten a meal to enjoy the smell and colour of the food. To be amongst this rainbow of colours, this melange of tactile objects,this collection which is a thing of beauty in its own right - often that is enough to refresh my soul.
Calling our collections a 'stash' reduces it to something waiting to be beautiful, it conveys the idea that objects have to have a purpose and function to be valid. The wonderful yarns, fibres and fabrics we have today do not need any validation of that kind. To exist gives pleasure. More is not required.