Yes, I do. I keep it in large plastic boxes in a spare room, organised into yarn weight with one box for my “best” yarns. These are the lovely hanks of wool I have bought over time from independent spinners and dyers, online or at shows.
If go to London for the day. I usually try to fit in a visit to Loop in Camden Passage, Islington and inevitably end up buying more yarn.
Last year, I did sell some yarns I had bought with specific projects in mind but years later, knew I was unlikely ever to get around to doing them.
Once a year, I bag up all the odds and ends and offer them on Freecycle. They are usually taken by people who knit toys, twiddlemuffs, crochet granny squares or amigurumi.