What would constitute stash, as in how long would one need to have had it sat marinating (love that term @datcat23) in their drawer/closet/storage box for it to be official stash? Not stuff we bought last week, presumably.
LOL ... you are welcome, although I wouldn't claim to be the first to coin that term.
How long before you consider fabric as a stash? My thoughts are it depends on how long it is stored. So if I buy fabric last week, and then it sits on the cutting table, is cut up and made .... then that is new fabric. However, if I buy fabric, I bring it home, wash it, fold it and put it in the fabric cupboard, then it is officially stash. Even if I have identified it as having a purpose, if it goes into storage, then its stash.
BTW, I can understand the aversion to the word "stash". I would imagine that for some, it has connotations of something illicit, or not allowed. We are grown adults ..... we shouldn't feel guilty about what we purchase, as long as the purchasing isn't itself a cause for concerns for yourself.
Oldest fabric in the stash? I not sure I subscribe to the prime minister unit of measure .... however I do have a few pieces of dead lady fabric, which probably date back to the 70's. I have a bolt of 1930's polished cotton I picked up from an antique consignment store. Its purchase was the cause of much distress for the seller, as she was mortified that I would not be "storing the fabric for posterity" and instead planned to ...*gasp* cut it up and sew with it.
So my advice would be ...... regardless of whether its Stash, Future Proofing, Fabric Archive, Retirement Fund, or Doomsday prepping ....... its just fabric, and you should sew it up. She who dies with the most fabric, dies anyway.
Sew it!