For me I had a stack dvd blanks left over, I decided to save a little bit of money and used them to back up folders of childhood photos, documents etc and place them inside their own jewel cases.
I do have a 2TB external HDD, But that I throw on LARGE steam game back ups and movies.
Sure, the “cloud” exists and I use that too but what if your intewebz goes down, good luck getting your backups until it’s back up.
What do you use? Optical media, tape drives etc?
A few years ago I went through a 15-year-old collection of DVDs and a surprising number of the burned discs were no longer usable.
Size-wise I’d probably just get a handful of 256 gig USB sticks and make multiple copies keep them in a temperature and humidity controlled environment.
USB sticks are only rated for 10 years. So you should only expect 5. Physically they will last much longer but the electrons leak out of the floating gate unless re-written.
I usually wrap my USBs in a few layers of tape to reduce the leakage