I rarely keep things for a long time unless I use it regularly, but I know who the hoarder is. I think that in the garage or in the attic, you can usually organize pantry and think about how to arrange the space so that it's convenient to store various things here. Not all houses and apartments may have enough free space for this, so there are companies like this obe https://www.maine-storage.com/
that provide warehouses, rooms, containers for storing various things. Perhaps you need to think about this option?