Right now I’m creating a nightly restic snapshot of my server on borgbase and on some spare drives, and keeping the snapshots forever. There’s a ton of daily churn in my data though, between databases and logs and other files that don’t constitute ‘real data’ but might be needed to restore the app.
Back when I used OneDrive, it deleted an important but seldom used folder. It just wasn’t there anymore. No one noticed for 6 months, but luckily I had kept a backup each month so could restore it easily.
3 weeks is definitely not long enough for me to notice something missing, if it’s just a random chunk of my 700GB of important stuff. E.g. if a folder of my kids photos from 5 years ago suddenly disappeared, I probably wouldn’t notice it for months but would be devistated to find it missing when I eventually went looking for it.
I don’t host massive amounts of data. Just my contacts, calendars, grocery lists, rss feeds, that kind of stuff. All my pictures and movies are on my PC and backed up separately.