I've had memory sticks go bad. Hard disks seem much more reliable.
Now I use two external hard drives to make backups. Both identical. I use them in turn. I just backup everything. Keep one off site, and the other near to hand but not connected.
I also keep archival copies of stuff like my financial records, and scans of family photos etc. with online storage.
I stopped using DVDs for backup a while back. I was using them mostly for images, and the DVDs I burned 10 years ago are still working.
I used to have a list of the best CD / DVD media for backups bookmarked. It looks as if that page has gone. Plenty of info if you search online though. Even some of the media from manufacturers you would think are OK can be less than archival quality. It's worth checking.
They say that if data doesn't exist in three separate places, then it doesn't actually exist. . .