I build a small custom NAS with 2x20TB HDD in raid + SSD for nextcloud files and other apps and I maxed out everything in a couple of years only. I have to check now if I can fit 2 more 20-24TB drive in this compact beast, theoritically it could as I kept spare 3.5" slots and SATA input but I remember it was full of cables everywhere when I assemble it so it might be challenging.

If I had a house with a large basement I would just get a server rack and stack HDD like crazy. Unfortunatelly (or fortunatelly) I cannot currently, it must fit in a furniture under the TV so I might need to delete some movies and series I will for sure not watch again, if possible easy to find ones first.