Sync is not a backup
This is important enough to make its own little FAQ topic. Let me quote one of the developers:
Warning: Brave does not officially support using the Sync code as a backup and you should not rely on this continuing to work in to the future. Use the export functionality in bookmarks and the password manager instead.
Let me be very clear here, the Sync Code changes daily. It’s always possible they may change how that works again in the future. The vital part here is that everyone realize you won’t be able to just write down the phrase, stash it away, and be able to rely on it to restore your information in the future. Unfortunately, that’s not what they want Sync to be used for.
Temporary Solution for expired phrase
At the time of writing this FAQ, there is a workaround for anyone who might not have been aware of this in the past. However, there’s no guarantee of when this link will stop working. So I highly recommend you don’t rely on it. The workaround at the time of writing this is that only the 25th word changes and you simply need to replace it. The current 25th word is found at https://alexeybarabash.github.io/25th-brave-sync-word/
–NOTE–
Don’t rely on that link. I know it’s tempting and it might last a while, but it will eventually change. Anyone who relies on it and thinks it lasts permanently might be in for a rude awakening if one day they come to use it to restore their data and they can’t.
Why does this code expire on a daily basis?
There have been a lot of instances where people have accidentally shared QR codes or phrases, whether it be here or on other platforms. They even had people who were scanning the QR code listed at https://support.brave.com/hc/en-us/articles/360021218111-How-do-I-set-up-Sync- which had been an active QR code to a dummy account, but as people scanned it they shared and accessed information with other users.
Seeing that lack of common sense and the security risk, Brave decided it was necessary to have it expire on a regular basis so that information is better protected. Unfortunately it’s always the small percentage of people who ruin it for the majority.