I would not stash lines of fabric, personally. If I like them I buy them for a particular project (which may not happen for some time - I guess that makes it stash eventually
). My "stash" is all fabric found on sale which (hopefully) I can mix & match later. As others have said, I tend to buy a bit over the requirement, so that becomes stash. And other than that, I haunt the sales and buy fabric that fits my "type" which I can use later (I'm a tone-on-tone quilter almost exclusively, so I'd never stash prints).